Bad character class exception on pattern that works for JDK's Pattern class

I'd like to use a email validation pattern that I came across on a Perl users
board.  It works just fine with Java's regex.Pattern class but fails to compile
when using Apache Regexp.  The RECompiler class returns a Bad character 
exception.  

The pattern I'm trying to use is:

^([0-9a-zA-Z]([-.\\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\\w]*[0-9a-zA-Z]\\.)+[a-zA-Z]
{2,9})$

If I strip out all the groups then RE will accept the pattern.  I know that RE
supports groups, but maybe not nested groups?