newbie question on adding tools to vbulletin

[Dismounted]

Not hard at all if the output can be taken directly from your Perl script. As mentioned by yourself, a cURL call or similar can be made to get the content. Assuming the authentication DB is MySQL and the vBulletin DB user has [read] access to it, the verification should also be simple.

Have a look in the Articles section - especially at the one about creating a vBulletin-powered page.