[xsl] check the type of the $pattern argument to a regular expression?

["bryan rasmussen" <rasmussen.bryan@xxxxxxxxx>]

Hi,

I would like to check the that the $pattern argument to a regular
expression in fact follows regular expression rules, since regex is
not castable I guess the only way to do this would be to use regular
expressions and perhaps a for-each to check that the $pattern argument
conforms?

Cheers,
Bryan Rasmussen