> It looks to me as if a second round of evaluation is being done. > During the first round the "\"s would be removed leaving "[[0-9]+]". > > The second round would pair the first "[" with the first "]", the > one before the "+" and would make your character class be digits > or opening square bracket. The final square bracket would be literal. > > You may have to play with the number of backslashes, probably doubling > them though in some troff documents it was even necessary to tripling > them in order to have one preserved when it was needed.
Thank you, your explanation is plausible... I indeed already tried with some escaping before posting. I'll try harder. But in any case, doesn't it sound like a bug? Because a correct regular expression is not matching as it should. Thanks again.