I'm not a Perl RegEx expert, but what about Perl regexes isn't idempotent? Which features modify the external environment other than by returning matches? Even variable assignment would be idempotent unless the variable is both modified and affects the behavior of the regex.
> How idempotence has to do with anything? A regex match is supposed to return a result, not perform effects…
Correct, which is why I was asking why the GP wrote:
> I'm unable to see how the approach suggested in the paper could be made idempotent with Perl's regular expression engine while still maintaining linear performance.
