Variable: +ALPHANUMERIC-ASCII-ALPHABET+

Documentation

All the letters and numbers in 7 bit ASCII.

Source

(defvar +alphanumeric-ascii-alphabet+
  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
  "All the letters and numbers in 7 bit ASCII.")