This is not how this forum works. This is not a "Do my homework for me" forum.

We will gladly help you with the problems you have with your existing code. Please show us the code you have, and tell us exactly what problems you have with your code.

In addition, it might be helpful to include a (link to a) description of what a Ramachandran plot is for those not familiar with it. The more relevant information you provide, the easier it is for somebody to help you with the task at hand.

While I must agree that this wasn't a good way to ask a question, it really isn't as simple as a quick search in Wikipedia to find an appropriate module for this if you're unfamiliar with the domain. You'll still need to do some work on your own (or find someone else) but here's a few hints beyond the obvious:

• PerlMol -- a bit out of date
• Bio::PDB::Structure -- assumes PDB format
• Do it purely mathematically (checking the convention for +/-).

These will allow you to get the data (look for the word 'dihedral'). The actual plotting can be done with any of a number of modules (ie, this part is general so check CPAN).