use Acme::Roman;

    print I + II; # III, as expected

##</code><code>##

    use Acme::Roman;

    print I() + II(); # III

##</code><code>##

    $ perl -w -Ilib -MAcme::Roman -e 'my $x = I+II'
    Argument "II" isn't numeric in addition (+) at -e line 1.
    Argument "I" isn't numeric in addition (+) at -e line 1.

##</code><code>##

    $ perl -w -Ilib -MAcme::Roman -e 'print I+II'
    Name "main::I" used only once: possible typo at -e line 1.
    print() on unopened filehandle I at -e line 1.