Time::Piece, (was first released with perl v5.9.5), would solve this simply. 
#!/usr/bin/perl
use strict;
use warnings;
use Time::Piece;

my $datetimestring = "4/5/13 16:09";

my $t = Time::Piece->strptime($datetimestring, "%m/%d/%y %H:%M");

print $t->strftime("%b %d, %Y %H:%M:%S");

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Prints Apr 05, 2013 16:09:00

Chris

In reply to Re: formatting datetime with strftime by Cristoforo
in thread formatting datetime with strftime by mreaves

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