One approach would be to look at every line of the file and inspect that that line matches. A Perl program to inspect a certain line of a file would be:

use strict;
use Tie::File;

my $f = shift;
my $l = shift -1;

tie my @f => 'Tie::File' => $f;
print "$l: $f[$l]";
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Save that program as a file and then invoke it for every line:

perl -w gfarhat.pl testfile.txt 1
perl -w gfarhat.pl testfile.txt 2
...
perl -w gfarhat.pl testfile.txt 9998
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You can golf the above program into the following, if the overhead of creating a Perl program is too much for you:

perl -nle 'BEGIN{$l=pop}print if $.==$l' testfile.txt 1
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