A lot of very clever people have been working hard to replace Perl's confusing mish-mash of date and time modules with a consistant set of modules. The results of their labours are at http://datetime.perl.org/ and you can get all of their modules from CPAN.

Using their modules, you can solve your problem like this:

#!/usr/bin/perl

use strict;
use warnings;

use DateTime::Format::Strptime;

my $strp = DateTime::Format::Strptime->new(pattern => '%b %d %Y %I:%M%
+p');

my $string = 'Dec 11 2003 12:00AM';

my $dt = $strp->parse_datetime($string) or die;

$string = $dt->strftime('%m/%d/%Y'); # warning! illogical format!!

print "$string\n";
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