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- PerlMol -- a bit out of date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).
