NAME

Error::Return - return(), skipping a scope

VERSION

version 1.100850

SYNOPSIS

use Error ':try';
use Error::Return;

sub doit {
    print " in doit, before try\n";
    try {
        print "  in try: start\n";
        RETURN 456;
        print "  in try: end\n";
    } catch Error with {
        my $E = shift;
        print "  caught error [$E]\n";
    };
    print " in doit, after try\n";
}

print "before doit\n";
my $x = doit();
print "doit() returned [$x]\n";
print "after doit\n";

# prints:
#
# before doit
#  in doit, before try
#   in try: start
# doit() returned [456]
# after doit

DESCRIPTION

The Error module provides try(), which takes a coderef using the & prototype so it looks more like a normal Perl block or like map() or grep(). But the "block" is still just an anonymous subroutine, so using return within the sub won't do what you think it will do. For example:

sub doit {
    print " in doit, before try\n";
    try {
        print "  in try: start\n";
        return 456;
        print "  in try: end\n";
    } catch Error with {
        my $E = shift;
        print "  caught error [$E]\n";
    };
    print " in doit, after try\n";
}

print "before doit\n";
my $x = doit();
print "doit() returned [$x]\n";
print "after doit\n";

The return in the try block (we call it a block, but it really isn't) looks like it should return from doit(), but it doesn't - it just returns from the anonymous sub that was passed to try(). Therefore, this program prints the following:

before doit
 in doit, before try
  in try: start
 in doit, after try
doit() returned [1]
after doit

So in doit, after try is still reached, and doit() returns 1 because of its last print statement.

While that is the correct behaviour, it is unintuitive. This module provides a more powerful way of returning.

METHODS

RETURN

Like return except that it doesn't just return to its upper scope but smashes right through it to the next-higher scope. Actually, it skips two scopes, because it has to return from the try() subroutine as well. It does take care of the cleanup that try() would normally perform.

See the synopsis as an example - this way, the try block will "do what you mean".

INSTALLATION

See perlmodinstall for information and options on installing Perl modules.

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests through the web interface at http://rt.cpan.org/Public/Dist/Display.html?Name=Error-Return.

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit http://www.perl.com/CPAN/ to find a CPAN site near you, or see http://search.cpan.org/dist/Error-Return/.

The development version lives at http://github.com/hanekomu/Error-Return/. Instead of sending patches, please fork this project using the standard git and github infrastructure.

AUTHOR

Marcel Gruenauer <marcel@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2009 by Marcel Gruenauer.

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