http://www.perlmonks.org?node_id=785241


in reply to Re^2: qr// and user provided regex patterns...
in thread qr// and user provided regex patterns...

I suspect that qr was not intended to be used on an entire subsitution operator like that. I believe it should only be used on the regular expression portion (left side) of the subsitution. See perlop.

Here is an example script which uses s/// as a command-line option:
http://www.cpan.org/authors/id/F/FO/FORMAN/ren-regexp-1.5