Hello Chris, thanks for the examples. They show that by adding anchors, the meaning of regular expressions is no longer compositional. For example (^|a) accepts the empty word only if no characters have been read yet. So (^|a) =~ "" does hold but a(^|a) =~ "a" does not hold although a =~ "a" does. I deem compositionality an important property to compare the current implementation with its specification. As, currently, I don't know how to incorporate anchors without making a mess, I refrain from adding them for the moment.
A more complicated use, perhaps as part of a crazy parser: "(a(\n)?)(^|b)(c|$)"
That's a nice example and I don't know how to express this without anchors. Cheers, Sebastian -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)