Aside from adding a 1; to the bottom of the module,
the test worked for me with 5.8.7 on netbsd.

# vi Roman.pm
# perl -I. test.pl
IX + IX = 18
XI * IV = 44
II ** X = 1024
M - I = 999
Powers of II:
        1
        2
        4
        8
        16
        32
        64
        128
# perl -v

This is perl, v5.8.7 built for i386-netbsd-thread-multi