Whoops, sorry. That method is in CGI::Prototype::Hidden. The Hidden module inherits from CGI::Prototype and adds functionality because it has basic state information (i.e., where am I?). It gets that from a simple hidden field called _state which is the text version of the page name. You can call the hidden field whatever you like; you just need to write it to each page using wrapper.

The idea is that there could eventually be different modules for different state mechanisms. So there is a simple one for Hidden fields. In the future there may be one for Cookies or MangledURLs, etc.