Exten => +X. (how do I remove a + from the dialed number

Seems self explanatory enough. I get a call coming into my asterisk box - user dials +15551212, how do I look for that and change it to 15551212 ?

{EXTEN:1} will return 15551212.
See doc/channelvariables.txt for more about.

Cheers.

Marco Bruni