$x = `gzgrep $y <PATH>`;
if( not $x ) {
    $x= `gzgrep -i <TERM> <PATH>`;
}

##</code><code>##

$x = `gzgrep $y <PATH>` || `gzgrep -i <TERM> <PATH>`;

##</code><code>##

use strict;
use warnings;