Shell Programming and Scripting

#!/usr/bin/perl
use strict;
open FH,"<a.txt";
my($n1,$n2,$pre,$mid,$post);
while(<FH>)
{
	chomp;
	my @tmp=split(",",$_);
	for( my $i=0;$i<=$#tmp;$i++){
		if ($tmp[$i] eq "working"){
			$n1=$i;
			next;
		}
		if ($tmp[$i] eq "protection"){
			$n2=$i;
			next;
		}
	}
	$pre=join ",",@tmp[0..$n1];
	$mid=join "-",@tmp[$n1+1..$n2-1];
	$post=join "-",@tmp[$n2+1..$#tmp];
	print $pre;
	print ",",$mid if $mid ne "";
	print ",",$tmp[$n2] if $tmp[$n2] ne "";
	print ",",$post if $post ne "";
	print "\n";
}