G'day tqisjim,

I changed this a few times as you posted updates. Anyway, here lowercase() contains one line, doesn't use temporary arrays, doesn't require other functions and returns the values you show in "Three conditions:" (using the same lowercase(...) calls).

$ perl -Mstrict -Mwarnings -E '
    sub lowercase {
        return (map { lc } @_)[wantarray ? (0 .. $#_) : 0];
    }

    my (@me, $me);
    @me = lowercase( qw( TQIS Jim ) ) ;  ## returns qw( tqis jim )
    say "@me";
    $me = lowercase( q{Jim} ) ;           ## returns q{jim}
    say "$me";
    @me = lowercase( qw( Jim ) ) ;       ## returns qw( jim )
    say "@me";
'
tqis jim
jim
jim
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Update: It would appear that, amidst all the various updates, I missed Re: wantarray alternative (Context propagation) by ++LanX which is a virtually identical solution but with a somewhat cleverer idiom:

(map { lc } @_)[0 .. wantarray * $#_]
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