How can this occur?

This is output from an RSpec test...

       expected: /<(?<tag>([[:alpha:]])+)>(?<cdata>(.)*)<\/\k<tag>>/
                 got: /<(?<tag>([[:alpha:]])+)>(?<cdata>(.)*)<\/\k<tag>>/
(using ==)

Any clue what I'm missing here?

Thanks,
Hal