Hi,
"..In our server there is no stricts and warning in stalled @INC hence unable to use this in my test script..."
strict and warnings comes installed with your perl installation. strict since perl 5 and warnings since perl v5.6.0. So if your perl version is newer than the ones i mentioned then you have these pragma installed.
Just use like so

use warnings;
use strict;
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in your perl scripts.
Moreso, I wonder why you are using a oneliner perl with a backtick while you can do all that very simply and clearly like so:
*

use warnings;
use strict;

for my $file ( glob("*.pl") ) {
    open my $fh, '<', $file or die $!;
    while ( defined( $_ = <$fh> ) ) {
        print $_;
        print "adding value=key\n" if $. == 3;
    }
}
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* Update