p6.p6

sub infix:<orelse>(+a) {
    my $ai := a.iterator;
    my Mu $current := $ai.pull-one;
    return Nil if $current =:= IterationEnd;

    nqp::until(
        (($_ := $ai.pull-one) =:= IterationEnd),
        nqp::stmts(
            nqp::if(
                $current.defined,
                nqp::stmts(
                    nqp::if( $current.WHAT === Code, $current := $current() ),
                    return $current,
                ),
            ),
            ($current := $_ ~~ Callable
                ?? (.count ?? $_($current) !! $_())
                !! $_
            ),
        ),
        :nohandler, # do not handle control stuff in thunks
    );

    $current.WHAT === Code ?? $current() !! $current
}

# cpan@perlbuild2~/CPANPRC/rakudo (nom)$ ./perl6 -e 'note (Int andthen "foo" orelse Int);'
# -> ;; $_ is raw { #`(Block|70927672) ... }