Error::Return - return(), skipping a scope
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
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:
try()
&
map()
grep()
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";
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:
try
doit()
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.
in doit, after try
1
print
While that is the correct behaviour, it is unintuitive. This module provides a more powerful way of returning.
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".
No bugs have been reported.
Please report any bugs or feature requests through the web interface at http://rt.cpan.org.
See perlmodinstall for information and options on installing Perl modules.
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//. Instead of sending patches, please fork this project using the standard git and github infrastructure.
Marcel Grünauer, <marcel@cpan.org>
<marcel@cpan.org>
Copyright 2009 by Marcel Grünauer
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Error::Return, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Error::Return
CPAN shell
perl -MCPAN -e shell install Error::Return
For more information on module installation, please visit the detailed CPAN module installation guide.