Conditional Cs?

[Michael Lazzaro]

Forgive me; a very minor style & efficiency question... what would the 
canonical way to do this be, given what we know of Perl6?

    # the hapless, inefficient version:
    ...
    return &result_of_some_big_long_calculation(...args...)
        if &result_of_some_big_long_calculation(...args...);
    ...
The obvious answers are this:

    my bool $x = &result_of_some_big_long_calculation(...args...);
    return $x if $x;
-or the identical -

    my bool $x;
    return $x if $x = &result_of_some_big_long_calculation(...args...);
Is there a way that doesn't require the named variable?  Perhaps using 
C<when>?  Just a thought experiment on my part, reduced from some code 
examples that do this sort of thing in a duplicitous fashion, 
switch-like...

    my bool $x;
    return $x if $x = &calc_try_1(...);
    return $x if $x = &calc_try_2(...);
    return $x if $x = &calc_try_3(...);
    ...
MikeL