The ~ operator has to decide whether to treat the scalar as a string or as a numeric. I would say it makes a lot of sense to prefer numeric treatment whenever that flag's set - as it's likely that a number that's also string is really a stringified number, and not that likely that it's a numified string.

So long as any XS or otherwise non-Perl code plays by the same rule, you're not going to run into trouble with that situation.

Makeshifts last the longest.