#!/usr/bin/perl
use strict;
use warnings;

my $big_dna = 'TGAACCCGGGATTTGAGATTCCGGGGTTAAAAACGATTGAACCCGGGATTTGAGATTCCGGGGTTAAAAA';
my $cutter = 'GATT';

my @cutted_parts;

{
  open(my $vh, '<', \$big_dna);
  local $/=$cutter;
  @cutted_parts=<$vh>;
  chomp(@cutted_parts);
  close($vh);
}

print "$_\n" for(@cutted_parts);