[1,2,10].map(&:to_s(16)) # => ["1", "2", "a"]

to_proc_with_args.patch

Index: parse.y
===================================================================
--- parse.y (revision 34892)
+++ parse.y (working copy)
@@ -2543,6 +2543,10 @@ block_arg	: tAMPER arg_value
 			$$ = $2;
 		    %*/
 		    }
+		| tAMPER literal paren_args
+		    {
+			$$ = NEW_BLOCK_PASS(NEW_CALL($2, rb_intern("to_proc"), $3));
+		    }
 		;
 
 opt_block_arg	: ',' block_arg
Index: string.c
===================================================================
--- string.c (revision 34892)
+++ string.c (working copy)
@@ -7515,6 +7515,27 @@ sym_call(VALUE args, VALUE sym, int argc, VALUE *argv)
     return rb_funcall_passing_block(obj, (ID)sym, argc - 1, argv + 1);
 }
 
+static VALUE
+sym_call2(VALUE arg, VALUE args, int argc, VALUE *argv)
+{
+    VALUE obj;
+    VALUE method;
+    int i;
+
+    if (argc < 1) {
+	rb_raise(rb_eArgError, "no receiver given");
+    }
+    obj = argv[0];
+
+    args = rb_ary_dup(args);
+    method = rb_ary_shift(args);
+    for (i = 1; i < argc; i++) {
+	rb_ary_push(args, argv[i]);
+    }
+
+    return rb_funcall_passing_block(obj, SYM2ID(method), RARRAY_LEN(args), RARRAY_PTR(args));
+}
+
 /*
  * call-seq:
  *   sym.to_proc
@@ -7525,13 +7546,23 @@ sym_call(VALUE args, VALUE sym, int argc, VALUE *argv)
  */
 
 static VALUE
-sym_to_proc(VALUE sym)
+sym_to_proc(int argc, VALUE *argv, VALUE sym)
 {
     static VALUE sym_proc_cache = Qfalse;
     enum {SYM_PROC_CACHE_SIZE = 67};
     VALUE proc;
     long id, index;
     VALUE *aryp;
+    VALUE args;
+
+    if (argc > 0) {
+	args = rb_ary_new2(argc + 1);
+	rb_ary_push(args, sym);
+	for (index = 0; index < argc; index++) {
+	    rb_ary_push(args, argv[index]);
+	}
+	return rb_proc_new(sym_call2, args);
+    }
 
     if (!sym_proc_cache) {
 	sym_proc_cache = rb_ary_tmp_new(SYM_PROC_CACHE_SIZE * 2);
@@ -7909,7 +7940,7 @@ Init_String(void)
     rb_define_method(rb_cSymbol, "id2name", rb_sym_to_s, 0);
     rb_define_method(rb_cSymbol, "intern", sym_to_sym, 0);
     rb_define_method(rb_cSymbol, "to_sym", sym_to_sym, 0);
-    rb_define_method(rb_cSymbol, "to_proc", sym_to_proc, 0);
+    rb_define_method(rb_cSymbol, "to_proc", sym_to_proc, -1);
     rb_define_method(rb_cSymbol, "succ", sym_succ, 0);
     rb_define_method(rb_cSymbol, "next", sym_succ, 0);