Don't use the browser...use Webservice::Validator::HTML::W3C

According to the perldoc there is a way to have the validator locally on your machine (doesn't say how though):

validator_uri
...

If you have a local installation of the validator ( recommended if you
+ wish to do a lot of testing ) or wish to use a validator at another 
+location then you can use this option.
[download]

Also, read the perldoc's OTHER MODULES section.