It depends on what you're trying to do. If your stored procedures are going to be doing all of your validation, what is your (Perl|C) part going to do? Just simple form handling and passing off the data to the database?

I'm not going to go into a comprehensive "Perl v. C" document, since there are dozens of them out there that do a far more complete job than I could here. In this specific case, though, Perl offers a benefit of rapid development time, in that there are modules already in place to do both the CGI stuff and database stuff, so a script to glue those two together in the form of a simple form processor would be pretty easy to write. If this is going to be something that is going to be hit pretty hard by a large number of requests, or if you already have staff on hand better equipped to maintain something in C, that might be your best bet.

Depending upon the complexity of your features, using the appropriate modules in Perl, you can write a script to do this task very fast with very few lines of code. I'm not familiar enough with C to know how much reusable libraries you can use to perform some of the lower level tasks (parsing the CGI stuff and interacting with the database).