[asterisk-users] Matching *, + and # in the dialplan

[Karl Fife]

In several places online, and in the Asterisk F.O.T. book, there is a
warning against using '_.' saying: 
"[it] should probably never be used".

However, the need often arises act on numeric extensions that begin with
*'s and #'s, and '+', and of course _X. does not match 

I have tried  exten => _[0-9*#+]. but that seems to be the functional
equivalent to _X. ignoring the addition of +,* and #.

Can someone suggest the best way to deal with this without resoring to a
highly repetitive/iterative dialplan?

Thanks in advance!

-Karl