+ { $$ = NULL; }
+ ;
+
+
+
+/* --------------------------------------
+ * subroutine signature parsing
+ */
+
+/* the '' or 'foo' part of a '$' or '@foo' etc signature variable */
+sigvarname: /* NULL */
+ { parser->in_my = 0; $$ = NULL; }
+ | PRIVATEREF
+ { parser->in_my = 0; $$ = $1; }
+ ;
+
+sigslurpsigil:
+ '@'
+ { $$ = '@'; }
+ | '%'
+ { $$ = '%'; }
+
+/* @, %, @foo, %foo */
+sigslurpelem: sigslurpsigil sigvarname sigdefault/* def only to catch errors */
+ {
+ I32 sigil = $1;
+ OP *var = $2;
+ OP *defexpr = $3;
+
+ if (parser->sig_slurpy)
+ yyerror("Multiple slurpy parameters not allowed");
+ parser->sig_slurpy = (char)sigil;
+
+ if (defexpr)
+ yyerror("A slurpy parameter may not have "
+ "a default value");
+
+ $$ = var ? newSTATEOP(0, NULL, var) : NULL;
+ }
+ ;
+
+/* default part of sub signature scalar element: i.e. '= default_expr' */
+sigdefault: /* NULL */
+ { $$ = NULL; }
+ | ASSIGNOP
+ { $$ = newOP(OP_NULL, 0); }
+ | ASSIGNOP term
+ { $$ = $2; }
+
+
+/* subroutine signature scalar element: e.g. '$x', '$=', '$x = $default' */
+sigscalarelem:
+ '$' sigvarname sigdefault
+ {
+ OP *var = $2;
+ OP *defexpr = $3;
+
+ if (parser->sig_slurpy)
+ yyerror("Slurpy parameter not last");
+
+ parser->sig_elems++;
+
+ if (defexpr) {
+ parser->sig_optelems++;
+
+ if ( defexpr->op_type == OP_NULL
+ && !(defexpr->op_flags & OPf_KIDS))
+ {
+ /* handle '$=' special case */
+ if (var)
+ yyerror("Optional parameter "
+ "lacks default expression");
+ op_free(defexpr);
+ }
+ else {
+ /* a normal '=default' expression */
+ OP *defop = (OP*)alloc_LOGOP(OP_ARGDEFELEM,
+ defexpr,
+ LINKLIST(defexpr));
+ /* re-purpose op_targ to hold @_ index */
+ defop->op_targ =
+ (PADOFFSET)(parser->sig_elems - 1);
+
+ if (var) {
+ var->op_flags |= OPf_STACKED;
+ (void)op_sibling_splice(var,
+ NULL, 0, defop);
+ scalar(defop);
+ }
+ else
+ var = newUNOP(OP_NULL, 0, defop);
+
+ LINKLIST(var);
+ /* NB: normally the first child of a
+ * logop is executed before the logop,
+ * and it pushes a boolean result
+ * ready for the logop. For ARGDEFELEM,
+ * the op itself does the boolean
+ * calculation, so set the first op to
+ * it instead.
+ */
+ var->op_next = defop;
+ defexpr->op_next = var;
+ }
+ }
+ else {
+ if (parser->sig_optelems)
+ yyerror("Mandatory parameter "
+ "follows optional parameter");
+ }
+
+ $$ = var ? newSTATEOP(0, NULL, var) : NULL;
+ }
+ ;
+
+
+/* subroutine signature element: e.g. '$x = $default' or '%h' */
+sigelem: sigscalarelem
+ { parser->in_my = KEY_sigvar; $$ = $1; }
+ | sigslurpelem
+ { parser->in_my = KEY_sigvar; $$ = $1; }
+ ;
+
+/* list of subroutine signature elements */
+siglist:
+ siglist ','
+ { $$ = $1; }
+ | siglist ',' sigelem
+ {
+ $$ = op_append_list(OP_LINESEQ, $1, $3);