Possible to determine new file name mhonarc just created?

Hello,

The problem is: I call mhonarc from a perl script to add
exactly one message a time to an archiv. Now I want to know the
name of the file mhonarc has created for this message.

One solution I know is to search all existing message files in an
archive for the subject, from , ... . But this is slow.

Any suggestions?

Thanks,

Silvester R"o"sner