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

my %exampledata= (
	ATTTA  => 'TTTAA',
	ATGTA  => 'ATGTA',
	ATGATG => 'ATGATG',
);

while (my($s1, $s2)= each %exampledata) {
	print $s1,'+',$s2,' => ',merge_data($s1, $s2),"\n";
}

##</code><code>##

sub merge_data {
	local($_)= join("-", @_);
	s/(.+)-\1/$1/;
	return $_;
}

##</code><code>##

sub merge_data {
	local($_)= join("-", @_);
	my($m_str)= $_;
	if (s/(.+)-\1/$1/) {
		my $first_result= $_;
		my $chop_off= length($_[0])-length($1)+1;
		$_= substr($m_str, $chop_off);
		if (s/(.+)-\1/$1/) {
			return substr($m_str, 0, $chop_off) . $_;
		}
		return $first_result;
	}
	return $_;
}

##</code><code>##

sub merge_data {
	local($_)= join("-", @_);
	my($m_str)= $_;
	if (s/(.+)-\1/$1/) {
		my $first_result= $_;
		my $chop_off= length($_[0])-length($1)+1;
		$_= substr($m_str, $chop_off);
		if (s/(.{2,})-\1/$1/) {
			return substr($m_str, 0, $chop_off) . $_;
		}
		return $first_result;
	}
	return $_;
}