Using closures for regex control

[Me]

[modified repost due to warnock's dilemma]

Would something like these DWIM?

    # match pat1 _ pat2 and capture pat2 match:
    / pat1 { ($foo) = / pat2 / } /

    # match pat1 _ 'foo bar':
    / pat1 { 'foo bar' } /

    # match pat2 if not pat1
    / { ! /pat1/ } pat2 } /

    # match pat2 if pat1 behind
    / { .lookbehind /pat1/ } pat2 } /

--
ralph