diff --git a/core/src/core_macros.rs b/core/src/core_macros.rs
new file mode 100644
index 0000000..d5ada8f
--- /dev/null
+++ b/core/src/core_macros.rs
@@ -0,0 +1,102 @@
+/// Define and reexport submodules.
+#[macro_export] macro_rules! modules(
+    ($($($feat:literal?)? $name:ident),* $(,)?) => { $(
+        $(#[cfg(feature=$feat)])? mod $name;
+        $(#[cfg(feature=$feat)])? pub use self::$name::*;
+    )* };
+    ($($($feat:literal?)? $name:ident $body:block),* $(,)?) => { $(
+        $(#[cfg(feature=$feat)])? mod $name $body
+        $(#[cfg(feature=$feat)])? pub use self::$name::*;
+    )* };
+);
+
+/// Define a trait an implement it for read-only wrapper types. */
+#[macro_export] macro_rules! flex_trait (
+    ($Trait:ident $(<$($A:ident:$T:ident),+>)? $(:$dep:ident $(+$dep2:ident)*)? {
+        $(fn $fn:ident (&$self:ident $(, $arg:ident:$ty:ty)*) -> $ret:ty $body:block)*
+    }) => {
+        pub trait $Trait $(<$($A: $T),+>)? $(:$dep$(+$dep2)*)? {
+            $(fn $fn (&$self $(,$arg:$ty)*) -> $ret $body)*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for &_T_ {
+            $(fn $fn (&$self $(,$arg:$ty)*) -> $ret { (*$self).$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for &mut _T_ {
+            $(fn $fn (&$self $(,$arg:$ty)*) -> $ret { (**$self).$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Arc<_T_> {
+            $(fn $fn (&$self $(,$arg:$ty)*) -> $ret { (*$self).$fn($($arg),*) })*
+        }
+        //impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for Option<_T_> {
+            //$(fn $fn (&$self $(,$arg:$ty)*) -> $ret {
+                //if let Some(this) = $self { this.$fn($($arg),*) } else { Ok(None) }
+            //})*
+        //}
+        //impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Mutex<_T_> {
+            //$(fn $fn (&$self $(,$arg:$ty)*) -> $ret { (*$self).lock().unwrap().$fn($($arg),*) })*
+        //}
+        //impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::RwLock<_T_> {
+            //$(fn $fn (&$self $(,$arg:$ty)*) -> $ret { $self.read().unwrap().$fn($($arg),*) })*
+        //}
+    });
+
+/// Define a trait an implement it for various mutation-enabled wrapper types. */
+#[macro_export] macro_rules! flex_trait_mut (
+    ($Trait:ident $(<$($A:ident:$T:ident),+>)? {
+        $(fn $fn:ident (&mut $self:ident $(, $arg:ident:$ty:ty)*) -> $ret:ty $body:block)*
+    })=>{
+        pub trait $Trait $(<$($A: $T),+>)? {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret $body)*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for &mut _T_ {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { (*$self).$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for Option<_T_> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret {
+                if let Some(this) = $self { this.$fn($($arg),*) } else { Ok(None) }
+            })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Mutex<_T_> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.get_mut().unwrap().$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Arc<::std::sync::Mutex<_T_>> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.lock().unwrap().$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::RwLock<_T_> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.write().unwrap().$fn($($arg),*) })*
+        }
+        impl<$($($A: $T,)+)? _T_: $Trait $(<$($A),+>)?> $Trait $(<$($A),+>)? for ::std::sync::Arc<::std::sync::RwLock<_T_>> {
+            $(fn $fn (&mut $self $(,$arg:$ty)*) -> $ret { $self.write().unwrap().$fn($($arg),*) })*
+        }
+    };
+);
+
+/// Implement [`Debug`] in bulk.
+#[macro_export] macro_rules! impl_debug(($($S:ty|$self:ident,$w:ident|$body:block)*)=>{
+    $(impl std::fmt::Debug for $S {
+        fn fmt (&$self, $w: &mut std::fmt::Formatter) -> std::fmt::Result $body
+    })* });
+
+/// Implement [`From`] in bulk.
+#[macro_export] macro_rules! from(
+    ($(<$($lt:lifetime),+>)?|$state:ident:$Source:ty|$Target:ty=$cb:expr) => {
+        impl $(<$($lt),+>)? From<$Source> for $Target {
+            fn from ($state:$Source) -> Self { $cb }}};
+    ($($Struct:ty { $(
+        $(<$($l:lifetime),* $($T:ident$(:$U:ident)?),*>)? ($source:ident: $From:ty) $expr:expr
+    );+ $(;)? })*) => { $(
+        $(impl $(<$($l),* $($T$(:$U)?),*>)? From<$From> for $Struct {
+            fn from ($source: $From) -> Self { $expr } })+ )* }; );
+
+/// Implement [Has].
+#[macro_export] macro_rules! has(($T:ty: |$self:ident : $S:ty| $x:expr) => {
+    impl Has<$T> for $S {
+        fn get (&$self) -> &$T { &$x }
+        fn get_mut (&mut $self) -> &mut $T { &mut $x } } };);
+
+/// Implement [MaybeHas].
+#[macro_export] macro_rules! maybe_has(
+    ($T:ty: |$self:ident : $S:ty| $x:block; $y:block $(;)?) => {
+        impl MaybeHas<$T> for $S {
+            fn get (&$self) -> Option<&$T> $x
+            fn get_mut (&mut $self) -> Option<&mut $T> $y } };);
diff --git a/core/src/lib.rs b/core/src/lib.rs
index b06b55e..0c63c05 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,38 +1,13 @@
+mod core_macros;
 pub(crate) use std::error::Error;
 /// Standard result type.
 pub type Usually<T> = Result<T, Box<dyn Error>>;
 /// Standard optional result type.
 pub type Perhaps<T> = Result<Option<T>, Box<dyn Error>>;
-/// Implement [`Debug`] in bulk.
-#[macro_export] macro_rules! impl_debug(($($S:ty|$self:ident,$w:ident|$body:block)*)=>{
-    $(impl std::fmt::Debug for $S {
-        fn fmt (&$self, $w: &mut std::fmt::Formatter) -> std::fmt::Result $body
-    })* });
-/// Implement [`From`] in bulk.
-#[macro_export] macro_rules! from(
-    ($(<$($lt:lifetime),+>)?|$state:ident:$Source:ty|$Target:ty=$cb:expr) => {
-        impl $(<$($lt),+>)? From<$Source> for $Target {
-            fn from ($state:$Source) -> Self { $cb }}};
-    ($($Struct:ty { $(
-        $(<$($l:lifetime),* $($T:ident$(:$U:ident)?),*>)? ($source:ident: $From:ty) $expr:expr
-    );+ $(;)? })*) => { $(
-        $(impl $(<$($l),* $($T$(:$U)?),*>)? From<$From> for $Struct {
-            fn from ($source: $From) -> Self { $expr } })+ )* }; );
 /// Type-dispatched `get` and `get_mut`.
 pub trait Has<T>: Send + Sync { fn get (&self) -> &T; fn get_mut (&mut self) -> &mut T; }
-/// Implement [Has].
-#[macro_export] macro_rules! has(($T:ty: |$self:ident : $S:ty| $x:expr) => {
-    impl Has<$T> for $S {
-        fn get (&$self) -> &$T { &$x }
-        fn get_mut (&mut $self) -> &mut $T { &mut $x } } };);
 /// Type-dispatched `get` and `get_mut` that return an [Option]-wrapped result.
 pub trait MaybeHas<T>: Send + Sync { fn get (&self) -> Option<&T>; fn get_mut (&mut self) -> Option<&mut T>; }
-/// Implement [MaybeHas].
-#[macro_export] macro_rules! maybe_has(
-    ($T:ty: |$self:ident : $S:ty| $x:block; $y:block $(;)?) => {
-        impl MaybeHas<$T> for $S {
-            fn get (&$self) -> Option<&$T> $x
-            fn get_mut (&mut $self) -> Option<&mut $T> $y } };);
 /// May compute a `RetVal` from `Args`.
 pub trait Eval<Args, RetVal> {
     /// A custom operation on [Args] that may return [Result::Err] or [Option::None].
diff --git a/dsl/src/dsl.rs b/dsl/src/dsl.rs
index 530e4f5..979585d 100644
--- a/dsl/src/dsl.rs
+++ b/dsl/src/dsl.rs
@@ -1,46 +1,81 @@
 //#![feature(adt_const_params)]
 //#![feature(type_alias_impl_trait)]
+#![feature(if_let_guard)]
 #![feature(impl_trait_in_fn_trait_return)]
 #![feature(const_precise_live_drops)]
 extern crate const_panic;
 use const_panic::PanicFmt;
 use std::fmt::Debug;
-pub(crate) use ::tengri_core::*;
+
 pub(crate) use std::error::Error;
+pub(crate) use std::sync::Arc;
+
 pub(crate) use konst::string::{str_range, char_indices};
 pub(crate) use thiserror::Error;
+pub(crate) use ::tengri_core::*;
+
 pub(crate) use self::DslError::*;
 
-mod dsl_conv;  pub use self::dsl_conv::*;
-mod dsl_types; pub use self::dsl_types::*;
-#[cfg(test)] mod dsl_test;
+mod dsl_conv;
+pub use self::dsl_conv::*;
 
-pub trait Dsl: Debug + Send + Sync + Sized {
-    fn src (&self) -> &str;
-}
+mod dsl_parse;
+pub(crate) use self::dsl_parse::*;
+pub mod parse { pub use crate::dsl_parse::*; }
 
-impl<'s> Dsl for &'s str {
-    fn src (&self) -> &str { self }
-}
+#[cfg(test)]
+mod dsl_test;
 
-impl Dsl for String {
-    fn src (&self) -> &str { self.as_str() }
-}
-
-impl Dsl for std::sync::Arc<str> {
+flex_trait!(Dsl: Debug + Send + Sync + Sized {
+    fn src (&self) -> &str {
+        unreachable!("Dsl::src default impl")
+    }
+});
+impl Dsl for Arc<str> {
+    fn src (&self) -> &str { self.as_ref() }
+}
+impl<'s> Dsl for &'s str {
     fn src (&self) -> &str { self.as_ref() }
 }
-
 impl<D: Dsl> Dsl for Option<D> {
     fn src (&self) -> &str { if let Some(dsl) = self { dsl.src() } else { "" } }
 }
 
-impl<D: Dsl> Dsl for &D {
-    fn src (&self) -> &str { (*self).src() }
+impl<D: Dsl> DslExp for D {}
+pub trait DslExp: Dsl {
+    fn exp (&self) -> DslPerhaps<&str> {
+        Ok(exp_peek(self.src())?)
+    }
+    fn head (&self) -> DslPerhaps<&str> {
+        Ok(peek(&self.src()[1..])?)
+    }
+    fn tail (&self) -> DslPerhaps<&str> {
+        Ok(if let Some((head_start, head_len)) = seek(&self.src()[1..])? {
+            peek(&self.src()[(1+head_start+head_len)..])?
+        } else {
+            None
+        })
+    }
 }
 
-impl<D: Dsl> Dsl for &mut D {
-    fn src (&self) -> &str { (**self).src() }
+impl<D: Dsl> DslSym for D {}
+pub trait DslSym: Dsl {
+    fn sym (&self) -> DslPerhaps<&str> { crate::parse::sym_peek(self.src()) }
+}
+
+impl<D: Dsl> DslKey for D {}
+pub trait DslKey: Dsl {
+    fn key (&self) -> DslPerhaps<&str> { crate::parse::key_peek(self.src()) }
+}
+
+impl<D: Dsl> DslText for D {}
+pub trait DslText: Dsl {
+    fn text (&self) -> DslPerhaps<&str> { crate::parse::text_peek(self.src()) }
+}
+
+impl<D: Dsl> DslNum for D {}
+pub trait DslNum: Dsl {
+    fn num (&self) -> DslPerhaps<&str> { crate::parse::num_peek(self.src()) }
 }
 
 /// DSL-specific result type.
diff --git a/dsl/src/dsl_types.rs b/dsl/src/dsl_parse.rs
similarity index 56%
rename from dsl/src/dsl_types.rs
rename to dsl/src/dsl_parse.rs
index 0a5402d..25eef20 100644
--- a/dsl/src/dsl_types.rs
+++ b/dsl/src/dsl_parse.rs
@@ -6,13 +6,13 @@ macro_rules! iter_chars(($source:expr => |$i:ident, $c:ident|$val:expr)=>{
 
 macro_rules! def_peek_seek(($peek:ident, $seek:ident, $seek_start:ident, $seek_length:ident)=>{
     /// Find a slice corrensponding to a syntax token.
-    const fn $peek (source: &str) -> DslPerhaps<&str> {
+    pub const fn $peek (source: &str) -> DslPerhaps<&str> {
         match $seek(source) {
             Ok(Some((start, length))) => Ok(Some(str_range(source, start, start + length))),
             Ok(None) => Ok(None),
             Err(e) => Err(e) } }
     /// Find a start and length corresponding to a syntax token.
-    const fn $seek (source: &str) -> DslPerhaps<(usize, usize)> {
+    pub const fn $seek (source: &str) -> DslPerhaps<(usize, usize)> {
         match $seek_start(source) {
             Ok(Some(start)) => match $seek_length(str_range(source, start, source.len() - start)) {
                 Ok(Some(length)) => Ok(Some((start, length))),
@@ -22,31 +22,10 @@ macro_rules! def_peek_seek(($peek:ident, $seek:ident, $seek_start:ident, $seek_l
             Ok(None) => Ok(None),
             Err(e) => Err(e) } } });
 
-const fn is_whitespace (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t') }
-
-pub trait DslExp: Dsl {
-    fn exp (&self) -> DslPerhaps<impl DslExp> {
-        todo!();
-        Ok(Some(self))
-    }
-    fn exp_head (&self) -> DslPerhaps<impl Dsl> {
-        todo!();
-        Ok(Some(self))
-    }
-    fn exp_tail (&self) -> DslPerhaps<impl DslExp> {
-        todo!();
-        Ok(Some(self))
-    }
-    fn exp_next (&mut self) -> DslPerhaps<impl Dsl> {
-        todo!();
-        Ok(Some(self))
-    }
-}
-impl<D: Dsl> DslExp for D {}
 def_peek_seek!(exp_peek, exp_seek, exp_seek_start, exp_seek_length);
-const fn is_exp_start (c: char) -> bool { matches!(c, '(') }
-const fn is_exp_end (c: char) -> bool { matches!(c, ')') }
-const fn exp_seek_start (mut source: &str) -> DslPerhaps<usize> {
+pub const fn is_exp_start (c: char) -> bool { matches!(c, '(') }
+pub const fn is_exp_end (c: char) -> bool { matches!(c, ')') }
+pub const fn exp_seek_start (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_exp_start(c) {
         return Ok(Some(i))
     } else if !is_whitespace(c) {
@@ -54,7 +33,7 @@ const fn exp_seek_start (mut source: &str) -> DslPerhaps<usize> {
     });
     Ok(None)
 }
-const fn exp_seek_length (mut source: &str) -> DslPerhaps<usize> {
+pub const fn exp_seek_length (mut source: &str) -> DslPerhaps<usize> {
     let mut depth = 0;
     iter_chars!(source => |i, c| if is_exp_start(c) {
         depth += 1;
@@ -70,13 +49,11 @@ const fn exp_seek_length (mut source: &str) -> DslPerhaps<usize> {
     Ok(None)
 }
 
-pub trait DslSym: Dsl { fn sym (&self) -> DslPerhaps<&str> { sym_peek(self.src()) } }
-impl<D: Dsl> DslSym for D {}
 def_peek_seek!(sym_peek,  sym_seek,  sym_seek_start,  sym_seek_length);
-const fn is_sym_start (c: char) -> bool { matches!(c, ':'|'@') }
-const fn is_sym_char (c: char) -> bool { matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-') }
-const fn is_sym_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
-const fn sym_seek_start (mut source: &str) -> DslPerhaps<usize> {
+pub const fn is_sym_start (c: char) -> bool { matches!(c, ':'|'@') }
+pub const fn is_sym_char (c: char) -> bool { matches!(c, 'a'..='z'|'A'..='Z'|'0'..='9'|'-') }
+pub const fn is_sym_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
+pub const fn sym_seek_start (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_sym_start(c) {
         return Ok(Some(i))
     } else if !is_whitespace(c) {
@@ -84,7 +61,7 @@ const fn sym_seek_start (mut source: &str) -> DslPerhaps<usize> {
     });
     Ok(None)
 }
-const fn sym_seek_length (mut source: &str) -> DslPerhaps<usize> {
+pub const fn sym_seek_length (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_sym_end(c) {
         return Ok(Some(i))
     } else if !is_sym_char(c) {
@@ -93,13 +70,11 @@ const fn sym_seek_length (mut source: &str) -> DslPerhaps<usize> {
     Ok(None)
 }
 
-pub trait DslKey: Dsl { fn key (&self) -> DslPerhaps<&str> { key_peek(self.src()) } }
-impl<D: Dsl> DslKey for D {}
 def_peek_seek!(key_peek,  key_seek,  key_seek_start,  key_seek_length);
-const fn is_key_start (c: char) -> bool { matches!(c, '/'|'a'..='z') }
-const fn is_key_char (c: char) -> bool { matches!(c, 'a'..='z'|'0'..='9'|'-'|'/') }
-const fn is_key_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
-const fn key_seek_start (mut source: &str) -> DslPerhaps<usize> {
+pub const fn is_key_start (c: char) -> bool { matches!(c, '/'|'a'..='z') }
+pub const fn is_key_char (c: char) -> bool { matches!(c, 'a'..='z'|'0'..='9'|'-'|'/') }
+pub const fn is_key_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
+pub const fn key_seek_start (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_key_start(c) {
         return Ok(Some(i))
     } else if !is_whitespace(c) {
@@ -107,7 +82,7 @@ const fn key_seek_start (mut source: &str) -> DslPerhaps<usize> {
     });
     Ok(None)
 }
-const fn key_seek_length (mut source: &str) -> DslPerhaps<usize> {
+pub const fn key_seek_length (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_key_end(c) {
         return Ok(Some(i))
     } else if !is_key_char(c) {
@@ -116,12 +91,10 @@ const fn key_seek_length (mut source: &str) -> DslPerhaps<usize> {
     Ok(None)
 }
 
-pub trait DslText: Dsl { fn text (&self) -> DslPerhaps<&str> { text_peek(self.src()) } }
-impl<D: Dsl> DslText for D {}
 def_peek_seek!(text_peek, text_seek, text_seek_start, text_seek_length);
-const fn is_text_start (c: char) -> bool { matches!(c, '"') }
-const fn is_text_end (c: char) -> bool { matches!(c, '"') }
-const fn text_seek_start (mut source: &str) -> DslPerhaps<usize> {
+pub const fn is_text_start (c: char) -> bool { matches!(c, '"') }
+pub const fn is_text_end (c: char) -> bool { matches!(c, '"') }
+pub const fn text_seek_start (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_text_start(c) {
         return Ok(Some(i))
     } else if !is_whitespace(c) {
@@ -129,15 +102,13 @@ const fn text_seek_start (mut source: &str) -> DslPerhaps<usize> {
     });
     Ok(None)
 }
-const fn text_seek_length (mut source: &str) -> DslPerhaps<usize> {
+pub const fn text_seek_length (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_text_end(c) { return Ok(Some(i)) });
     Ok(None)
 }
 
-pub trait DslNum: Dsl { fn num (&self) -> DslPerhaps<&str> { num_peek(self.src()) } }
-impl<D: Dsl> DslNum for D {}
 def_peek_seek!(num_peek,  num_seek,  num_seek_start,  num_seek_length);
-const fn num_seek_start (mut source: &str) -> DslPerhaps<usize> {
+pub const fn num_seek_start (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_digit(c) {
         return Ok(Some(i));
     } else if !is_whitespace(c) {
@@ -145,7 +116,7 @@ const fn num_seek_start (mut source: &str) -> DslPerhaps<usize> {
     });
     Ok(None)
 }
-const fn num_seek_length (mut source: &str) -> DslPerhaps<usize> {
+pub const fn num_seek_length (mut source: &str) -> DslPerhaps<usize> {
     iter_chars!(source => |i, c| if is_num_end(c) {
         return Ok(Some(i))
     } else if !is_digit(c) {
@@ -153,8 +124,8 @@ const fn num_seek_length (mut source: &str) -> DslPerhaps<usize> {
     });
     Ok(None)
 }
-const fn is_digit (c: char) -> bool { matches!(c, '0'..='9') }
-const fn is_num_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
+pub const fn is_digit (c: char) -> bool { matches!(c, '0'..='9') }
+pub const fn is_num_end (c: char) -> bool { matches!(c, ' '|'\n'|'\r'|'\t'|')') }
 pub const fn to_number <D: Dsl> (digits: &str) -> Result<usize, DslError> {
     let mut iter = char_indices(digits);
     let mut value = 0;
@@ -174,3 +145,39 @@ pub const fn to_digit (c: char) -> Result<usize, DslError> {
         _ => return Err(Unexpected(c))
     })
 }
+
+pub const fn peek (mut src: &str) -> DslPerhaps<&str> {
+    Ok(Some(match () {
+        _ if let Ok(Some(exp))  = exp_peek(src) => exp,
+        _ if let Ok(Some(sym))  = sym_peek(src) => sym,
+        _ if let Ok(Some(key))  = key_peek(src) => key,
+        _ if let Ok(Some(num))  = num_peek(src) => num,
+        _ if let Ok(Some(text)) = text_peek(src) => text,
+        _ => {
+            iter_chars!(src => |_i, c| if !is_whitespace(c) {
+                return Err(Unexpected(c))
+            });
+            return Ok(None)
+        }
+    }))
+}
+
+pub const fn seek (mut src: &str) -> DslPerhaps<(usize, usize)> {
+    Ok(Some(match () {
+        _ if let Ok(Some(exp))  = exp_seek(src) => exp,
+        _ if let Ok(Some(sym))  = sym_seek(src) => sym,
+        _ if let Ok(Some(key))  = key_seek(src) => key,
+        _ if let Ok(Some(num))  = num_seek(src) => num,
+        _ if let Ok(Some(text)) = text_seek(src) => text,
+        _ => {
+            iter_chars!(src => |_i, c| if !is_whitespace(c) {
+                return Err(Unexpected(c))
+            });
+            return Ok(None)
+        }
+    }))
+}
+
+pub const fn is_whitespace (c: char) -> bool {
+    matches!(c, ' '|'\n'|'\r'|'\t')
+}
diff --git a/input/src/input_command.rs b/input/src/input.rs
similarity index 50%
rename from input/src/input_command.rs
rename to input/src/input.rs
index 6051277..7b451ee 100644
--- a/input/src/input_command.rs
+++ b/input/src/input.rs
@@ -1,5 +1,25 @@
 use crate::*;
 
+/// Event source
+pub trait Input: Sized {
+    /// Type of input event
+    type Event;
+    /// Result of handling input
+    type Handled; // TODO: make this an Option<Box dyn Command<Self>> containing the undo
+    /// Currently handled event
+    fn event (&self) -> &Self::Event;
+    /// Whether component should exit
+    fn is_done (&self) -> bool;
+    /// Mark component as done
+    fn done (&self);
+}
+
+flex_trait_mut!(Handle <E: Input> {
+    fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
+        Ok(None)
+    }
+});
+
 pub trait Command<S>: Send + Sync + Sized {
     fn execute (self, state: &mut S) -> Perhaps<Self>;
     fn delegate <T> (self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
diff --git a/input/src/input_dsl.rs b/input/src/input_dsl.rs
index 0bec9a8..bb3c353 100644
--- a/input/src/input_dsl.rs
+++ b/input/src/input_dsl.rs
@@ -1,8 +1,10 @@
 use crate::*;
+
 /// Map of each event (e.g. key combination) to
 /// all command expressions bound to it by
 /// all loaded input layers.
 type EventMapImpl<E, C> = BTreeMap<E, Vec<Binding<C>>>;
+
 /// A collection of input bindings.
 ///
 /// Each contained layer defines a mapping from input event to command invocation
@@ -14,8 +16,27 @@ type EventMapImpl<E, C> = BTreeMap<E, Vec<Binding<C>>>;
 /// that .event()binding's value is returned.
 #[derive(Debug)]
 pub struct EventMap<E, C>(EventMapImpl<E, C>);
+
+/// An input binding.
+#[derive(Debug, Clone)]
+pub struct Binding<C> {
+    pub command:     C,
+    pub condition:   Option<Condition>,
+    pub description: Option<Arc<str>>,
+    pub source:      Option<Arc<PathBuf>>,
+}
+
+/// Input bindings are only returned if this evaluates to true
+#[derive(Clone)]
+pub struct Condition(Arc<Box<dyn Fn()->bool + Send + Sync>>);
+
+impl_debug!(Condition |self, w| { write!(w, "*") });
+
 /// Default is always empty map regardless if `E` and `C` implement [Default].
-impl<E, C> Default for EventMap<E, C> { fn default () -> Self { Self(Default::default()) } }
+impl<E, C> Default for EventMap<E, C> {
+    fn default () -> Self { Self(Default::default()) }
+}
+
 impl<E: Clone + Ord, C> EventMap<E, C> {
     /// Create a new event map
     pub fn new () -> Self {
@@ -28,7 +49,7 @@ impl<E: Clone + Ord, C> EventMap<E, C> {
     }
     /// Add a binding to an event map.
     pub fn add (&mut self, event: E, binding: Binding<C>) -> &mut Self {
-        if (!self.0.contains_key(&event)) {
+        if !self.0.contains_key(&event) {
             self.0.insert(event.clone(), Default::default());
         }
         self.0.get_mut(&event).unwrap().push(binding);
@@ -54,33 +75,49 @@ impl<E: Clone + Ord, C> EventMap<E, C> {
     }
     /// Create event map from string.
     pub fn from_source (source: impl AsRef<str>) -> Usually<Self> where E: From<Arc<str>> {
-        Self::from_dsl(source.as_ref())
+        Self::from_dsl(&mut source.as_ref())
     }
     /// Create event map from DSL tokenizer.
-    pub fn from_dsl (mut dsl: impl Dsl) -> Usually<Self> where E: From<Arc<str>> {
+    pub fn from_dsl <'s, > (dsl: &'s mut impl Dsl) -> Usually<Self> where E: From<Arc<str>> {
         let mut map: Self = Default::default();
-        while let Some(dsl) = dsl.exp_next()? {
-            if let Some(path) = dsl.text()? {
-                map.0.extend(Self::from_path(PathBuf::from(path.as_ref() as &str))?.0)
-            } else if dsl.exp_head()?.key()? == Some("if") {
-                todo!()
-                //map.add(sym.into(), Binding::from_dsl(dsl.exp_tail())?);
-            } else if let Some(sym) = dsl.exp_head()?.sym()? {
-                todo!()
-                //map.add(sym.into(), Binding::from_dsl(dsl.exp_tail())?);
+        if let Some(dsl) = dsl.exp()? {
+            let mut head = dsl.head()?;
+            let mut tail = dsl.tail()?;
+            loop {
+                if let Some(ref token) = head {
+                    if let Some(ref text) = token.text()? {
+                        map.0.extend(Self::from_path(PathBuf::from(text))?.0);
+                        continue
+                    }
+                    //if let Some(ref exp) = token.exp()? {
+                        ////_ if let Some(sym) = token.head()?.sym()?.as_ref() => {
+                            ////todo!()
+                        ////},
+                        ////_ if Some(&"if") == token.head()?.key()?.as_ref() => {
+                            ////todo!()
+                        ////},
+                        //return Err(format!("unexpected: {:?}", token.exp()).into())
+                    //}
+                    return Err(format!("unexpected: {token:?}").into())
+                } else {
+                    break
+                }
+                if let Some(next) = tail {
+                    head = next.head()?;
+                    tail = next.tail()?;
+                } else {
+                    break
+                }
             }
+        } else if let Some(text) = dsl.text()? {
+            todo!("load from file path")
+        } else {
+            todo!("return error for invalid input")
         }
         Ok(map)
     }
 }
-/// An input binding.
-#[derive(Debug)]
-pub struct Binding<C> {
-    pub command:     C,
-    pub condition:   Option<Condition>,
-    pub description: Option<Arc<str>>,
-    pub source:      Option<Arc<PathBuf>>,
-}
+
 impl<C> Binding<C> {
     fn from_dsl (dsl: impl Dsl) -> Usually<Self> {
         let mut command:     Option<C>            = None;
@@ -94,8 +131,6 @@ impl<C> Binding<C> {
         }
     }
 }
-pub struct Condition(Box<dyn Fn()->bool + Send + Sync>);
-impl_debug!(Condition |self, w| { write!(w, "*") });
 
 fn unquote (x: &str) -> &str {
     let mut chars = x.chars();
diff --git a/input/src/input_handle.rs b/input/src/input_handle.rs
deleted file mode 100644
index 2be276c..0000000
--- a/input/src/input_handle.rs
+++ /dev/null
@@ -1,77 +0,0 @@
-use crate::*;
-use std::sync::{Mutex, Arc, RwLock};
-
-/// Event source
-pub trait Input: Sized {
-    /// Type of input event
-    type Event;
-    /// Result of handling input
-    type Handled; // TODO: make this an Option<Box dyn Command<Self>> containing the undo
-    /// Currently handled event
-    fn event (&self) -> &Self::Event;
-    /// Whether component should exit
-    fn is_done (&self) -> bool;
-    /// Mark component as done
-    fn done (&self);
-}
-
-/// Implement the [Handle] trait.
-#[macro_export] macro_rules! handle {
-    (|$self:ident:$Struct:ty,$input:ident|$handler:expr) => {
-        impl<E: Engine> ::tengri::input::Handle<E> for $Struct {
-            fn handle (&mut $self, $input: &E) -> Perhaps<E::Handled> {
-                $handler
-            }
-        }
-    };
-    ($E:ty: |$self:ident:$Struct:ty,$input:ident|$handler:expr) => {
-        impl ::tengri::input::Handle<$E> for $Struct {
-            fn handle (&mut $self, $input: &$E) ->
-                Perhaps<<$E as ::tengri::input::Input>::Handled>
-            {
-                $handler
-            }
-        }
-    }
-}
-
-/// Handle input
-pub trait Handle<E: Input> {
-    fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
-        Ok(None)
-    }
-}
-impl<E: Input, H: Handle<E>> Handle<E> for &mut H {
-    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
-        (*self).handle(context)
-    }
-}
-impl<E: Input, H: Handle<E>> Handle<E> for Option<H> {
-    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
-        if let Some(handle) = self {
-            handle.handle(context)
-        } else {
-            Ok(None)
-        }
-    }
-}
-impl<H, E: Input> Handle<E> for Mutex<H> where H: Handle<E> {
-    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
-        self.get_mut().unwrap().handle(context)
-    }
-}
-impl<H, E: Input> Handle<E> for Arc<Mutex<H>> where H: Handle<E> {
-    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
-        self.lock().unwrap().handle(context)
-    }
-}
-impl<H, E: Input> Handle<E> for RwLock<H> where H: Handle<E> {
-    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
-        self.write().unwrap().handle(context)
-    }
-}
-impl<H, E: Input> Handle<E> for Arc<RwLock<H>> where H: Handle<E> {
-    fn handle (&mut self, context: &E) -> Perhaps<E::Handled> {
-        self.write().unwrap().handle(context)
-    }
-}
diff --git a/input/src/input_macros.rs b/input/src/input_macros.rs
index ae5758c..e47b902 100644
--- a/input/src/input_macros.rs
+++ b/input/src/input_macros.rs
@@ -1,10 +1,30 @@
-/** Implement `Command` for given `State` and `handler` */
+/// Implement [Command] for given `State` and `handler`
 #[macro_export] macro_rules! command {
     ($(<$($l:lifetime),+>)?|$self:ident:$Command:ty,$state:ident:$State:ty|$handler:expr) => {
-        impl$(<$($l),+>)? Command<$State> for $Command {
+        impl$(<$($l),+>)? ::tengri::input::Command<$State> for $Command {
             fn execute ($self, $state: &mut $State) -> Perhaps<Self> {
                 Ok($handler)
             }
         }
     };
 }
+
+/// Implement [Handle] for given `State` and `handler`.
+#[macro_export] macro_rules! handle {
+    (|$self:ident:$State:ty,$input:ident|$handler:expr) => {
+        impl<E: Engine> ::tengri::input::Handle<E> for $State {
+            fn handle (&mut $self, $input: &E) -> Perhaps<E::Handled> {
+                $handler
+            }
+        }
+    };
+    ($E:ty: |$self:ident:$State:ty,$input:ident|$handler:expr) => {
+        impl ::tengri::input::Handle<$E> for $State {
+            fn handle (&mut $self, $input: &$E) ->
+                Perhaps<<$E as ::tengri::input::Input>::Handled>
+            {
+                $handler
+            }
+        }
+    }
+}
diff --git a/input/src/input_test.rs b/input/src/input_test.rs
new file mode 100644
index 0000000..8373435
--- /dev/null
+++ b/input/src/input_test.rs
@@ -0,0 +1,28 @@
+use crate::*;
+
+#[test] fn test_stub_input () -> Usually<()> {
+    use crate::*;
+    struct TestInput(bool);
+    enum TestEvent { Test1 }
+    impl Input for TestInput {
+        type Event = TestEvent;
+        type Handled = ();
+        fn event (&self) -> &Self::Event {
+            &TestEvent::Test1
+        }
+        fn is_done (&self) -> bool {
+            self.0
+        }
+        fn done (&self) {}
+    }
+    let _ = TestInput(true).event();
+    assert!(TestInput(true).is_done());
+    assert!(!TestInput(false).is_done());
+    Ok(())
+}
+
+#[cfg(all(test, feature = "dsl"))] #[test] fn test_dsl_keymap () -> Usually<()> {
+    let _keymap = CstIter::new("");
+    Ok(())
+}
+
diff --git a/input/src/lib.rs b/input/src/lib.rs
index 0779092..f219c64 100644
--- a/input/src/lib.rs
+++ b/input/src/lib.rs
@@ -3,41 +3,14 @@
 
 pub(crate) use std::fmt::Debug;
 pub(crate) use std::sync::Arc;
-pub(crate) use std::collections::{BTreeMap, HashMap};
+pub(crate) use std::collections::BTreeMap;
 pub(crate) use std::path::{Path, PathBuf};
 pub(crate) use std::fs::exists;
 pub(crate) use tengri_core::*;
 
 mod input_macros;
-mod input_command; pub use self::input_command::*;
-mod input_handle;  pub use self::input_handle::*;
-
+mod input; pub use self::input::*;
 #[cfg(feature = "dsl")] pub(crate) use ::tengri_dsl::*;
 #[cfg(feature = "dsl")] mod input_dsl;
 #[cfg(feature = "dsl")] pub use self::input_dsl::*;
-
-#[cfg(test)] #[test] fn test_stub_input () -> Usually<()> {
-    use crate::*;
-    struct TestInput(bool);
-    enum TestEvent { Test1 }
-    impl Input for TestInput {
-        type Event = TestEvent;
-        type Handled = ();
-        fn event (&self) -> &Self::Event {
-            &TestEvent::Test1
-        }
-        fn is_done (&self) -> bool {
-            self.0
-        }
-        fn done (&self) {}
-    }
-    let _ = TestInput(true).event();
-    assert!(TestInput(true).is_done());
-    assert!(!TestInput(false).is_done());
-    Ok(())
-}
-
-#[cfg(all(test, feature = "dsl"))] #[test] fn test_dsl_keymap () -> Usually<()> {
-    let _keymap = CstIter::new("");
-    Ok(())
-}
+#[cfg(test)] mod input_test;
diff --git a/output/src/ops.rs b/output/src/ops.rs
index 846c86c..bdbcff0 100644
--- a/output/src/ops.rs
+++ b/output/src/ops.rs
@@ -373,7 +373,7 @@ transform_xy_unit!("padding/x" "padding/y" "padding/xy"|self: Padding, area|{
 /// the layout elements that are provided by this crate.
 #[cfg(feature = "dsl")] mod ops_dsl {
     use crate::*;
-    use ::tengri_dsl::*;
+    //use ::tengri_dsl::*;
 
     //macro_rules! dsl {
         //($(
diff --git a/proc/src/proc_flex.rs b/proc/src/proc_flex.rs
new file mode 100644
index 0000000..039dd7d
--- /dev/null
+++ b/proc/src/proc_flex.rs
@@ -0,0 +1,2 @@
+// TODO: #[derive(Flex, FlexMut, FlexOption, FlexResult ... ?)]
+// better derive + annotations
diff --git a/proc/src/proc_view.rs b/proc/src/proc_view.rs
index bd44c96..13a5d5c 100644
--- a/proc/src/proc_view.rs
+++ b/proc/src/proc_view.rs
@@ -56,13 +56,13 @@ impl ViewDef {
         let builtins = builtins_with_boxes_output(quote! { #output })
             .map(|(builtin, builtin_ty)|match builtin {
                 Single(name) => quote! {
-                    if dsl.exp_head()?.key()? == Some(#name) {
+                    if dsl.head()?.key()? == Some(#name) {
                         return Ok(Some(#builtin_ty::from_dsl_or_else(self, dsl,
                             ||format!("failed to load builtin").into())?.boxed()))
                     }
                 },
                 Prefix(name) => quote! {
-                    if let Some(key) = dsl.exp_head()?.key()? && key.starts_with(#name) {
+                    if let Some(key) = dsl.head()?.key()? && key.starts_with(#name) {
                         return Ok(Some(#builtin_ty::from_dsl_or_else(self, dsl,
                             ||format!("failed to load builtin").into())?.boxed()))
                     }