OK, I can't resist. I take it the signature for the original functionality can not change. It must change for the inverted functionality of course, unless you have a Vulcan Mind Meld interface. With that in mind, how about this?

sub find_string {
    my ( $file, $string, $negative ) = @_;
    return 1
        if _find_string( $file, $string, $negative )
    die "False :Test result is FAIL";
}

sub find_without_string {
    $_[2] = 1;
    goto &find_string;
}

sub _find_string {
    my ($file, $string, $negative) = @_;
    open my $fh, '<', $file;
    while (<$fh>) {
        return !$negative if /\Q$string/;
    }
    return $negative;
}

# Original functionality
find_string('search.txt', 'name: abc ');

# Inverted functionality
find_string('search2.txt', 'name: abc ', 1 );
# or
find_without_string('search2.txt', 'name: abc ' );

[download]

Of course, now that find_string() is a wrapper, you can play with the signature of _find_string() however you like. For example, you could pass it qr{\Q$string}, as was suggested earlier.

In reply to Re: Perl script to Parse a file for a string by Anonymous Monk
in thread Perl script to Parse a file for a string by user786

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