G'day onlyIDleft,

A good place to start might be "perlootut - Object-Oriented Programming in Perl Tutorial".

You might also like to follow the links from "Tutorials: Object Oriented Programming" here at PerlMonks. [Disclaimer: I haven't read any of these so I can't suggest what might be more appropriate for you.]

I'm not a user of BioPerl. You'll probably get much better answers from others. The BioPerl page on CPAN looks like a reasonable starting point: I note it has links to tutorials (but I can't comment on how good or current they are).