Shell Programming and Scripting

#!/usr/bin/perl

use strict;
use warnings;

while(my $line = <>){
        chomp $line;
        $line =~ s/\s+//g;
        my @cols = split(';',$line);
        my %hash;
        for(my $i=0;$i<=$#cols;$i++){
                if (exists $hash{$cols[$i]} && $hash{$cols[$i]} eq $cols[$i+1]){
                        print "$line is a repeat \n";
                        last;
                }
                else {
                        $hash{$cols[$i]} = $cols[$i+1];
                         $i++;
                }
        }
}