Well it can assign $_. My mistake above and your originally is that <> only assigns $_ if it is the only thing inside the conditional of a while loop. I guess after using it that way for years I forgot it was the only way!

I should have consulted the Camel before I posted my errors. The funny thing is what I posted does work sometimes (specifically it works with the two tests I used - there's a lesson there too), but also fails in unexpected (by me) ways.