Plugin callbacks in Perl

I'm working in Perl and I'm trying to make a script / plugin that is suppsed to use the OnPluginCommand function. However the example that is displayed on http://www.gammon.com.au/forum/bbshowpost.php?bbsubject_id=1692 is in VB and uses Function instead of Sub. Is there a way to do this in Perl? :)

Many thanks,
Simon

I think that in Perl, like other languages, everything is a function, so you don't have to do anything explicit about it, just return a value.