The qr// operator would be pretty lame if it didn't honor the modifiers that you compiled it with.

Yes, but that's a fair bit different than forcibly disabling the modifiers that you omitted...

What's surprising is not that qr/perl/i produces (?i:perl), but that it produces (?i-xsm:perl), with the other modifiers explicitly disabled.

That makes plenty of sense, but I'd never seen it explicitly documented before.