diff --git a/output/src/ops_dsl.rs b/output/src/ops_dsl.rs
index 196f693..5d131bb 100644
--- a/output/src/ops_dsl.rs
+++ b/output/src/ops_dsl.rs
@@ -3,7 +3,7 @@ use Value::*;
 
 impl<S, A> Dsl<S> for When<A> where S: Eval<Ast, bool> + Eval<Ast, A> {
     fn try_provide (state: &S, source: Ast) -> Perhaps<Self> {
-        if let Exp(_, exp) = source.0 && let Some(Ast(Key(id))) = exp.peek() && *id == *"when" {
+        if let Exp(_, mut exp) = source.0 && let Some(Ast(Key(id))) = exp.peek() && *id == *"when" {
             let _ = exp.next();
             return Ok(Some(Self(
                 state.eval(exp.next().unwrap(), ||"when: expected condition")?,
@@ -16,7 +16,7 @@ impl<S, A> Dsl<S> for When<A> where S: Eval<Ast, bool> + Eval<Ast, A> {
 
 impl<S, A, B> Dsl<S> for Either<A, B> where S: Eval<Ast, bool> + Eval<Ast, A> + Eval<Ast, B> {
     fn try_provide (state: &S, source: Ast) -> Perhaps<Self> {
-        if let Exp(_, exp) = source.0 && let Some(Ast(Key(id))) = exp.peek() && *id == *"either" {
+        if let Exp(_, mut exp) = source.0 && let Some(Ast(Key(id))) = exp.peek() && *id == *"either" {
             let _ = exp.next();
             return Ok(Some(Self(
                 state.eval(exp.next().unwrap(), ||"either: expected condition")?,
@@ -32,7 +32,7 @@ impl<S, A> Dsl<S> for Align<A> where S: Eval<Option<Ast>, A> {
     fn try_provide (state: &S, source: Ast) -> Perhaps<Self> {
         if let Exp(_, source) = source.0 {
             let mut rest = source.clone();
-            return Ok(Some(match rest.next().and_then(|x|x.key()) {
+            return Ok(Some(match rest.next().as_ref().and_then(|x|x.key()) {
                 Some("align/c")  => Self::c(state.eval(rest.next(),  ||"align/c: expected content")?),
                 Some("align/x")  => Self::x(state.eval(rest.next(),  ||"align/x: expected content")?),
                 Some("align/y")  => Self::y(state.eval(rest.next(),  ||"align/y: expected content")?),
@@ -55,7 +55,7 @@ impl<S, A, B> Dsl<S> for Bsp<A, B> where S: Eval<Option<Ast>, A> + Eval<Option<A
     fn try_provide (state: &S, source: Ast) -> Perhaps<Self> {
         if let Exp(_, exp) = source.0 {
             let mut rest = exp.clone();
-            return Ok(Some(match rest.next().and_then(|x|x.key()) {
+            return Ok(Some(match rest.next().as_ref().and_then(|x|x.key()) {
                 Some("bsp/n") => Self::n(
                     state.eval(rest.next(), ||"bsp/n: expected content 1")?,
                     state.eval(rest.next(), ||"bsp/n: expected content 2")?,