what (?x) are in use? (was RFC 145 (alternate approach))

[resent, 'cos I can't spell "perl6"]

Richard Proctor wrote:
:The whole (?x set of thingies is getting complicated...  The list of what is
:used at present (and in current suggestions is:
:
:Current Use in perl5
:
:(?#     comment
:(?imsx  flags
:(?-imsx flags

That's actually (?iogcmsx and (?-iogcmsx. ('o' is ignored; I'm not sure
what if any effect 'g' and 'c' have, but it probably ain't pretty.)

In theory, all letters should be reserved to map to future flags for
the same reason. That's why we've been accumulating multi-punctuation
signifiers, so it may be time to go for a new paradigm with more room
for expansion: (+keyword) or (*keyword) would seem to be candidates.

Hugo