I am having some trouble with the Regex callback architecture. Fist of all for, for a variable number of matches, the only way to code is with a callback function and for_each iterator, correct? To make it more interesting, I have a callback calling another callback. This could obviously go deeper and deeper. Due to the inflexibility (perhaps by me perceived?) of the callback architecture, I am forced to use a lot of global variables. To be fair, this is highly manageable within my current application, but I am concerned that this "implicit number and types of parameters" restriction may become a stumbling block in future code. At this stage, what I am trying to determine whether I should base my program(s) on (from simplest to more complex): - Regex - eXpressive - Spirit So far, I prefer Regex because it is much more stable than Spirit. The latter seems to have great potential, but when when I find that I am unable to even build the test examples properly, and the specs vary from one version to the next, I conclude that it is best to allow the good people of Spirit ("spirited people"? :-) time to deliver a more polished product. Don't know anything about eXpressive yet. Regards, -Ramon