Formsess developement: matching a variable in a string

Hello guys, I'm still working in order to improve formsess, my forms generation & validation library for smarty. At the moment, I'm attempting to cleanup the mess I have when dealing with variables inside formsess tags. To summarize, all the tags look like this: <fs:input type="text" name="foo" /> Of course, you are supposed to be able to use a smarty variable as the name. So I had to build a regexp in order to match smarty variables, but I'm realizing that it's quite stupid to reinvent the wheel, and it would be better to let smarty handle that. So, the actual question is: what method could I cleanly use in order to check if a string is a smarty variable, or a string containing a smarty variable with backticks ? Thanks in advance, Katana