sporadic ArrayIndexOutOfBoundsException?

All,

Using Oro 2.0.3, we're occasionally seeing an
ArrayIndexOutOfBoundsException emanating from 

	Perl5Matcher.__match(Perl5Matcher.java:859)

Or occasionally

	Perl5Matcher.__repeat(Perl5Matcher.java:762)

This happens only under heavy load & may be related to a threading
issue... my research is very preliminary at this point.

Before I dive in, has anyone seen this one before?  ...I didn't see
anything in release notes or Bugzilla.

I'm using a static instance of PatternCacheLRU, shared among different
threads... which, I suppose, means that the Patterns that it returns are
potentially shared too.  Does anyone know whether these objects are
thread-safe when used in this way?

-Matt