diff --git a/lib/Minilisp.pm b/lib/Minilisp.pm
index fde6a86..85ca69b 100644
--- a/lib/Minilisp.pm
+++ b/lib/Minilisp.pm
@@ -743,6 +743,25 @@ sub macro_unless {
 }
 $macros{unless} = \&macro_unless;
 
+sub macro_set {
+  my $ts = shift;
+
+  my $ident = parser_identifier($ts);
+
+  my $expr = parser_expr($ts);
+
+  return sub {
+    my $ctx = shift;
+
+    my $value = $expr->($ctx);
+
+    ctx_assign($ctx, $ident, $value);
+
+    return $value;
+  }
+}
+$macros{set} = \&macro_set;
+
 sub compile {
   my ($term) = @_;
   my @tokens = tokenize($term);
diff --git a/t/context.t b/t/context.t
new file mode 100644
index 0000000..e563538
--- /dev/null
+++ b/t/context.t
@@ -0,0 +1,12 @@
+(let ((a 2))
+  (let ((a 10))
+    (expect "Inner variable shadows outer" (= a 10)))
+  (expect "Outer is not overriden" (= a 2)))
+
+(let ((pings 0))
+  (defun ping ()
+      (set pings (+ pings 1)))
+
+  (ping) (ping) (ping)
+
+  (expect "setting variables in outside context works" (= pings 3)))