#!/usr/bin/perl

use strict;
use warnings;

my $string = 'a' x 50_000 . 'skjd';
my $regexp = qr-^((.){32000}\2{18000})skjd$-;

print "yes\n" if $string =~ /$regexp/;

my $regexp = qr-^((.{25000}){2})skjd$-;