Did you check that /etc/syslog.conf is comparable on both systems, i.e. that your message should generate a log message on bsd too ? Is a there a file to write the message into (there are syslogds that don't write to a log file if it doesn't exist already) ?

I would put an strace (or whatever bsd has for that) on syslogd. Whenever your program generates a message, you should see activity in that process. If yes, there is something wrong with syslogds config, if no, the fault lies with Sys::Syslog.