Data::FormValidator

So we can

• require a parameter be mandatory
• specify a parameter be optional
• constraint checking; builtins, regexs, sub, array
• default parameter values
• validate based on dependancies
• filter values, eg trim leading and trailing spaces

and returns

• object reference
• sets hash of valid parameters
  • valids
• sets arrays for error handling
  • missings
  • invalids
  • unknowns