[exim] Is this a bug?

Ok - This is weird. I have the following code in the acl_smtp_mail acl:

accept    condition = ${if match {$acl_c1}{"(white|yellow)"}}

warn     logwrite = TEST - $acl_c1

In theory, the accept should catch and strings with either the word
"white" or "yellow" in the string. But - strings with those words are
still getting through.

What am I missing?