Longest repeating sequence - PERL

#!/usr/bin/perl
 
 
#Name: text_longest_repeating_v1.pl
#
#Written by: Balazs, Lendvay (ITFanatic :) )
#
#Purpose: this script finds the longest repeating sequence in the only line in $file
#(the script was created to analyze a continous character string)
#
#The script can be downloaded from "ITFanatic.com" and it is absolutely FREE,
#you can redistribute it and/or modify it under the same terms as Perl itself. (I think:) )
#This script comes with NO WARRANTY of any kind. (I am sure! :) )
#I cannot guarantee that this works in your environment, and I am not responsible
#for any harm it may cause on your computer. (I hope it won't cause harm at all :) )
 
use strict;
my $file="test.txt";
 
my $starter=0;
my $maxi=2;
my $str="";
my $line="";
my $rep=0;
my $maxstr="";
my $maxrep=0;
#open file for read
open FILE0, $file or die "Cannot open $filename for read :$!";
 
#read file line which contains the string
while (<FILE0>) {
	$line=$_;
}
print "Line: $line\n";
#close file
close FILE0;
 
#cut the first two characters
$str=substr($line,$starter,$maxi);
 
#get the length of the line
my $len=length($line);
print "Length:".$len."\n";
#reset string which contains the remaining string
my $searchin="";
 
#repeat until the last string
while ($starter<($len-$maxi+1))
{
	#cut the string which is the pattern to search
	$str=substr($line,$starter,$maxi);
	#cut the remaining string to search in
	$searchin=substr($line,$starter+$maxi,$len);
	if ($searchin=~/$str/) 
	{
		#if string found increment counter
		$rep++;
	}
	else
	{
		#if string not found, reset counter
		$rep=0;
	}
	if (length($str)>length($maxstr) && ($rep==1))
	{
		#if string is repeated and the length is longer than the previous match
		#record string and length
		$maxrep=$rep;
		$maxstr=$str;
		#print the new longest string
		print "New max found: \"$maxstr\" , count: \"$maxrep\"\n";
	}
	if ($rep==1)
	{
		#if match found, increment maxi until you can
		$maxi++;
		$rep=0;
		$str="";
	}
	else
	{
		#if match not found, increment $starter, leave maxi at previous value
		$starter++;
		#just to see the process, print every 1000th loop the starter position
		my $mod=$starter % 1000;
		if ($mod eq 0)
		{
			print "Starter++ mod 1000: $starter\n";
		}
		$rep=0;
		$str="";
	}
 
}
print "Maximum string: \"$maxstr\" repeated: \"$maxrep\" \n";