if you have it installed, try

perl -MNet::SNMP -le"print for keys %INC"
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If you don't, you can take a look at the Makefile.PL on the search.cpan.org

but the best way is to read the README file which has a section called REQUIREMENTS that lists the requirements.

Update: if you want to know which shared object (.so) files are required by a Net::SNMP, this might help if you have it installed:

ldd /path/to/Net/SNMP.so (if it exists at all)
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