diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index 53ffdd87cb1..cb2df2a5a3e 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -162,6 +162,7 @@ tag expr_ {
     expr_ext(vec[@expr], option.t[@expr], ann);
     expr_fail;
     expr_ret(option.t[@expr]);
+    expr_put(option.t[@expr]);
     expr_be(@expr);
     expr_log(@expr);
     expr_check_expr(@expr);
diff --git a/src/comp/front/parser.rs b/src/comp/front/parser.rs
index 5ffaca197c3..a779d0133cd 100644
--- a/src/comp/front/parser.rs
+++ b/src/comp/front/parser.rs
@@ -638,6 +638,20 @@ impure fn parse_bottom_expr(parser p) -> @ast.expr {
             }
         }
 
+        case (token.PUT) {
+            p.bump();
+            alt (p.peek()) {
+                case (token.SEMI) {
+                    ex = ast.expr_put(none[@ast.expr]);
+                }
+                case (_) {
+                    auto e = parse_expr(p);
+                    hi = e.span;
+                    ex = ast.expr_put(some[@ast.expr](e));
+                }
+            }
+        }
+
         case (token.BE) {
             p.bump();
             auto e = parse_expr(p);
@@ -1420,6 +1434,7 @@ fn stmt_ends_with_semi(@ast.stmt stmt) -> bool {
                 case (ast.expr_path(_,_,_))     { ret true; }
                 case (ast.expr_fail)            { ret true; }
                 case (ast.expr_ret(_))          { ret true; }
+                case (ast.expr_put(_))          { ret true; }
                 case (ast.expr_be(_))           { ret true; }
                 case (ast.expr_log(_))          { ret true; }
                 case (ast.expr_check_expr(_))   { ret true; }
diff --git a/src/comp/middle/fold.rs b/src/comp/middle/fold.rs
index 4e8ea317451..4d3c2e2d149 100644
--- a/src/comp/middle/fold.rs
+++ b/src/comp/middle/fold.rs
@@ -154,6 +154,9 @@ type ast_fold[ENV] =
      (fn(&ENV e, &span sp,
          &option.t[@expr] rv) -> @expr)           fold_expr_ret,
 
+     (fn(&ENV e, &span sp,
+         &option.t[@expr] rv) -> @expr)           fold_expr_put,
+
      (fn(&ENV e, &span sp,
          @expr e) -> @expr)                       fold_expr_be,
 
@@ -640,6 +643,17 @@ fn fold_expr[ENV](&ENV env, ast_fold[ENV] fld, &@expr e) -> @expr {
             ret fld.fold_expr_ret(env_, e.span, oee);
         }
 
+        case (ast.expr_put(?oe)) {
+            auto oee = none[@expr];
+            alt (oe) {
+                case (some[@expr](?x)) {
+                    oee = some(fold_expr(env_, fld, x));
+                }
+                case (_) { /* fall through */  }
+            }
+            ret fld.fold_expr_put(env_, e.span, oee);
+        }
+
         case (ast.expr_be(?x)) {
             auto ee = fold_expr(env_, fld, x);
             ret fld.fold_expr_be(env_, e.span, ee);
@@ -1130,6 +1144,11 @@ fn identity_fold_expr_ret[ENV](&ENV env, &span sp,
     ret @respan(sp, ast.expr_ret(rv));
 }
 
+fn identity_fold_expr_put[ENV](&ENV env, &span sp,
+                               &option.t[@expr] rv) -> @expr {
+    ret @respan(sp, ast.expr_put(rv));
+}
+
 fn identity_fold_expr_be[ENV](&ENV env, &span sp, @expr x) -> @expr {
     ret @respan(sp, ast.expr_be(x));
 }
@@ -1396,6 +1415,7 @@ fn new_identity_fold[ENV]() -> ast_fold[ENV] {
          fold_expr_path   = bind identity_fold_expr_path[ENV](_,_,_,_,_),
          fold_expr_fail   = bind identity_fold_expr_fail[ENV](_,_),
          fold_expr_ret    = bind identity_fold_expr_ret[ENV](_,_,_),
+         fold_expr_put    = bind identity_fold_expr_put[ENV](_,_,_),
          fold_expr_be     = bind identity_fold_expr_be[ENV](_,_,_),
          fold_expr_log    = bind identity_fold_expr_log[ENV](_,_,_),
          fold_expr_check_expr
diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index e140ddccef1..c8f21dff513 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -3122,6 +3122,10 @@ fn trans_expr(@block_ctxt cx, @ast.expr e) -> result {
             ret trans_ret(cx, e);
         }
 
+        case (ast.expr_ret(?e)) {
+            ret trans_put(cx, e);
+        }
+
         case (ast.expr_be(?e)) {
             ret trans_be(cx, e);
         }
@@ -3199,6 +3203,11 @@ fn trans_fail(@block_ctxt cx, common.span sp, str fail_str) -> result {
     ret trans_upcall(cx, "upcall_fail", args);
 }
 
+fn trans_put(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
+    cx.fcx.ccx.sess.unimpl("put expr");
+    fail;
+}
+
 fn trans_ret(@block_ctxt cx, &option.t[@ast.expr] e) -> result {
     auto bcx = cx;
     auto val = C_nil();
diff --git a/src/comp/middle/ty.rs b/src/comp/middle/ty.rs
index 58529d0dc9c..f9b2bd9d000 100644
--- a/src/comp/middle/ty.rs
+++ b/src/comp/middle/ty.rs
@@ -691,6 +691,7 @@ fn expr_ty(@ast.expr expr) -> @t {
         case (ast.expr_log(_))                { ret plain_ty(ty_nil); }
         case (ast.expr_check_expr(_))         { ret plain_ty(ty_nil); }
         case (ast.expr_ret(_))                { ret plain_ty(ty_nil); }
+        case (ast.expr_put(_))                { ret plain_ty(ty_nil); }
         case (ast.expr_be(_))                 { ret plain_ty(ty_nil); }
     }
     fail;
diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index d0043c43940..5109adb2a43 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -1040,6 +1040,7 @@ fn demand_expr_full(&@fn_ctxt fcx, @ty.t expected, @ast.expr e,
         case (ast.expr_fail) { e_1 = e.node; }
         case (ast.expr_log(_)) { e_1 = e.node; }
         case (ast.expr_ret(_)) { e_1 = e.node; }
+        case (ast.expr_put(_)) { e_1 = e.node; }
         case (ast.expr_be(_)) { e_1 = e.node; }
         case (ast.expr_check_expr(_)) { e_1 = e.node; }
     }
@@ -1317,6 +1318,27 @@ fn check_expr(&@fn_ctxt fcx, @ast.expr expr) -> @ast.expr {
             }
         }
 
+        case (ast.expr_put(?expr_opt)) {
+            alt (expr_opt) {
+                case (none[@ast.expr]) {
+                    auto nil = plain_ty(ty.ty_nil);
+                    if (!are_compatible(fcx, fcx.ret_ty, nil)) {
+                        fcx.ccx.sess.err("put; in function "
+                                         + "putting non-nil");
+                    }
+
+                    ret expr;
+                }
+
+                case (some[@ast.expr](?e)) {
+                    auto expr_0 = check_expr(fcx, e);
+                    auto expr_1 = demand_expr(fcx, fcx.ret_ty, expr_0);
+                    ret @fold.respan[ast.expr_](expr.span,
+                                                ast.expr_put(some(expr_1)));
+                }
+            }
+        }
+
         case (ast.expr_be(?e)) {
             /* FIXME: prove instead of check */
             check ast.is_call_expr(e);