BEGIN {
    *call_to_inspect = ( rand() < 0.5
        ? sub ($) {}
        : sub (@) {}
    );
}

##</code><code>##

BEGIN {
    *call_to_query = ( rand() < 0.5
        ? sub ($) {}
        : sub (@) {}
    );
}

sub inspector { print wantarray ? 1 : 0, "\n" }
call_to_inspect(inspector());

##</code><code>##

>perl a.pl
1

>perl a.pl
1

>perl a.pl
0

>perl a.pl
1