#!/usr/bin/perl -w
use strict;
my @array=qw (5 4 10);
for(my $i=0;$i<$#array;$i++){
            my $first=$ar_no[$i];
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The code you posted does not compile:

Global symbol "@ar_no" requires explicit package name at
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You can use diagnostics to get a more verbose explanation. You declared an array name "array", but you did not declare an array named "ar_no". Try changing ar_no to array.