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

my $seq = "AATGGTTTCTCCCATCTCTCCATCGGCATAAAAATACAGAATGATCTAA";

my @beg;
push @beg, $-[0] while $seq =~ /ATG/g;

my @end;
push @end, $+[0] while $seq =~ /T(?:AG|AA|GA)/g;

my @data;
for my $i (@beg) {
	for my $j (@end) {
		next if $j-$i < 6;	
		push @data, substr $seq, $i, $j-$i;
	}
}

print "$_\n" for @data;

##</code><code>##

ATGGTTTCTCCCATCTCTCCATCGGCATAA
ATGGTTTCTCCCATCTCTCCATCGGCATAAAAATACAGAATGA
ATGGTTTCTCCCATCTCTCCATCGGCATAAAAATACAGAATGATCTAA
ATGATCTAA