sub proc{
    my ($file) = @_;
    # (...)
    my $pathC = $path . "/$file";
    open my $input, "zcat $pathC|"
        or do {
            print STDERR "\n!!ATTENTION:\n\tUnable to run zcat: $!\n";
            return;
        };

    while (my $line = <$input> ){
        # (...) data proccessing irrelevant to the problem
    }

    # Not needed. Will happen automatically
    # when $input goes out of scope.
    #close($input);
}