!/usr/bin/perl -w
use strict;
use warnings;
my $cmd;
my $cmd1;
$cmd = system("perl -pi -e 's/#//' test.txt"); # removing comments working
$cmd1 = system("perl -pi -e 's/(?=.*\btest\b)/#/' test.txt"); #Adding #'s is not working
print "$cmd \n";
print "$cmd1\n";