wantarray function

Get list vs array context of current subroutine call Returns TRUE if the context of the currently executing subroutine is looking for a list value. Returns FALSE if the context is looking for a scalar. Returns the undefined value if the context is looking for no value (void context). 

    return unless defined wantarray;    # don't bother doing more
    my @a = complex_calculation();
    return wantarray ? @a : "@a";