ERROR: Can't use global $1 in "my" at /usr/perl5/site_perl/5.005/base6

Greetings,

After installing MHonArc for the first time and running it for the
first time, I received and continue to receive the following error:

% mhonarc mailfile
This is MHonArc v2.6.9, Perl 5.00503 solaris
Converting messages to .
Reading mailfile
{.......................................................................
...........
Can't use global $1 in "my" at /usr/perl5/site_perl/5.005/base64.pl line
55,
<GEN0> chunk 9344.
%

Help requested; thank you in advance.