Use (?=) for success and (?!) for failure. That is easier to understand and more direct than \w\b\w. You end up with (?(?{ PERL-CODE }) (?=) | (?!) ). You can write only the failure condition by negating the result of the perl code: (? (?{ not PERL-CODE }) (?!) )

In reply to Re: Perl's regexp (?{...}) construct and constraining matches. by diotalevi
in thread Perl's regexp (?{...}) construct and constraining matches. by davido

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