ido: Regexp Matching

 
 2.4 Regular Expression Matching
 ===============================
 
 There is limited provision for regexp matching within Ido, enabled
 through ‘ido-enable-regexp’ (toggle with ‘C-t’).  This allows you to
 type ‘[ch]$’ for example and see all file names ending in ‘c’ or ‘h’.
 
  -- User Option: ido-enable-regexp
      If the value of this user option is non-‘nil’, Ido will do regexp
      matching.  The value of this user option can be toggled within
      ido-mode using ‘ido-toggle-regexp’.
 
    *Please notice:* Ido-style completion is inhibited when you enable
 regexp matching.