[xenophonf]

Is that a Common Lisp thing or something that predates the ANSI standard? SBCL doesn't like that syntax:

  * 10_000
  
  debugger invoked on a UNBOUND-VARIABLE: The variable |10_000| is unbound.

According to the Common Lisp HyperSpec, "_" is an alphabetic constituent character:

http://www.lispworks.com/documentation/HyperSpec/Body/02_ad....

http://www.lispworks.com/documentation/HyperSpec/Body/02_adb...