From the Perl6 summary for week 20030406 but it a slightly different context:

Dave Whipp pointed out that it would also be possible to write:

sub return_if_true ($value) {
    if $value {
        leave where => caller(1), value => $value;
    }
}

# and then just do:

return_if_true(result_of_big_long_calculation(...));
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I think the leave where => caller(1) is the double return I was curious about.

(p6language thread)