How does regex recursion and (?(DEFINE)) affect performance or memory usage?

Perl, regex, recursion, (?(DEFINE)), performance, memory usage

This article explores how regex recursion and (?(DEFINE)) in Perl can impact performance and memory usage, including practical examples to illustrate these concepts.


        <?php
        // Example of regex recursion with (?(DEFINE))
        $pattern = '/
            (?(DEFINE)
                (?&subroutine) 
                \(\?P<subroutine> [^()]* \)
            )
            (?&subroutine)
        /x';

        $string = '(your content here)';

        if (preg_match($pattern, $string, $matches)) {
            echo "Match found: " . print_r($matches, true);
        } else {
            echo "No match found.";
        }
        ?>