#!/usr/bin/perl 
use strict;
use warnings;
use File::Find;
use File::stat;
use DateTime;
use Time::localtime;
use Data::Dumper;

my %old_file;
my ( $dt1, $dt2 );
my ( $tm, $dur, $st);

$dt1 = new DateTime(
    year  => 2006,
    month => 1,
    day   => 1
);

find( \&wanted, '/home/user' );

sub wanted {
    if ( /[.] pl \z/x ) { 
     
        $st = stat( $File::Find::name ) or die "No file: $!"; 
        $tm = localtime( $st->mtime );
        $dt2 = new DateTime(
            year  => $tm->year + 1900,
            month => $tm->mon + 1,
            day   => $tm->mday
        );

        $dur = $dt1->subtract_datetime($dt2);
        $old_file{$_} = $dt2->ymd if $dur->is_positive;
    }   
}

print Dumper( \%old_file );