Return::MultiLevel(3) User Contributed Perl Documentation Return::MultiLevel(3)

Return::MultiLevel - Return across multiple call levels

version 0.08

use Return::MultiLevel qw(with_return);
sub inner {
  my ($f) = @_;
  $f->(42);  # implicitly return from 'with_return' below
  print "You don't see this\n";
sub outer {
  my ($f) = @_;
  print "You don't see this either\n";
my $result = with_return {
  my ($return) = @_;
  die "Not reached";
print $result, "\n";  # 42

This module provides a way to return immediately from a deeply nested call stack. This is similar to exceptions, but exceptions don't stop automatically at a target frame (and they can be caught by intermediate stack frames using "eval"). In other words, this is more like setjmp(3)/longjmp(3) than "die".

Another way to think about it is that the "multi-level return" coderef represents a single-use/upward-only continuation.

The following functions are available (and can be imported on demand).

Executes BLOCK, passing it a code reference (called $return in this description) as a single argument. Returns whatever BLOCK returns.

If $return is called, it causes an immediate return from "with_return". Any arguments passed to $return become "with_return"'s return value (if "with_return" is in scalar context, it will return the last argument passed to $return).

It is an error to invoke $return after its surrounding BLOCK has finished executing. In particular, it is an error to call $return twice.

This module uses "unwind" from "Scope::Upper" to do its work. If "Scope::Upper" is not available, it substitutes its own pure Perl implementation. You can force the pure Perl version to be used regardless by setting the environment variable "RETURN_MULTILEVEL_PP" to 1.

If you get the error message "Attempt to re-enter dead call frame", that means something has called a $return from outside of its "with_return { ... }" block. You can get a stack trace of where that "with_return" was by setting the environment variable "RETURN_MULTILEVEL_DEBUG" to 1.

You can't use this module to return across implicit function calls, such as signal handlers (like $SIG{ALRM}) or destructors ("sub DESTROY { ... }"). These are invoked automatically by perl and not part of the normal call chain.

  • Lukas Mai
  • Graham Ollis <>

This software is copyright (c) 2013,2014,2021 by Lukas Mai.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

2022-09-22 perl v5.36.0