After all ldkjdlkjf2098kklls probably isnt [[:alpha:]]+\d+[[:alpha:]]+
I did play around once with a small script that did these things, when I was bored, and no, it probably isn't. But what I did was take several strings and tried to derive a common expression out of them - first looking for similarities, like a sequence of numbers in the middle, or whitespace at the end, or whatever, and then built sub-regexes from the parts. I think starting with splitting on non-words and such gave so-so results for things like email addresses..
Of course, I never really got any really usable results, but it was a fun exercise. :) What I wanted to say was that do decide which it should be you need a decent sample of several strings that should all match. Then it is sometimes possible to get something to build upon. Maybe. :)
You have moved into a dark place.
It is pitch black. You are likely to be eaten by a grue. 