Well, for a start you could change the node title :-)

Seriously, I don't know where you could start from:

"defining a syntax" can be a big job if you want a language with a minimum of flexibility, or a trivial one if you have only a handful of commands to implement. It really depends on what your program should do, and you have not given much detail.

On the parser side, there are many choices available but I never did these things in Perl, so it's better for somebody else to advise you.