our( $foo, $bar, $qux);

$string =~ m[
    ( some regex ) (?{ $foo = $^N })
    other stuff
    ( a conditional capture ) (?{ $bar = $^N })
    |
    ( another possibility ) (?{ $bar = $^N })
    ...
    ( a final piece ) (?{ $qux = $^N })
]x;