subroutine signatures

Declarative syntax to unwrap argument list into lexical variables.
"sub foo ($a,$b) {...}" checks number of arguments and puts the
arguments into lexical variables.  Signatures are not equivalent to the
existing idiom of "sub foo { my($a,$b) = @_; ... }".  Signatures are only
available by enabling a non-default feature, and generate warnings about
being experimental.  The syntactic clash with prototypes is managed by
disabling the short prototype syntax when signatures are enabled.

1 files changed, 6 insertions, 0 deletions

diff --git a/feature.h b/feature.h
index c98a5b3294..698302c43f 100644
--- a/feature.h
+++ b/feature.h
@@ -80,6 +80,12 @@
 	 FEATURE_IS_ENABLED("arybase")) \
     )
 
+#define FEATURE_SIGNATURES_IS_ENABLED \
+    ( \
+	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
+	 FEATURE_IS_ENABLED("signatures") \
+    )
+
 #define FEATURE___SUB___IS_ENABLED \
     ( \
 	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_515 \