I'm seeking your opinion on whether the coding practice I adopt is a sound one and if not, how should I change it.

That wheel exists already in several forms. They're all more flexible than your solution (which you'll get sick of maintaining in a short time). Pleas read up on Data::FormValidator, CGI::FormBuilder, CGI::Untaint, even Params::Validate. And don't forget to combine Regexp::Common with these when appropriate.