Synopsis:
   $rindex(<characters> <text>)

Technical:
   * If the <characters> argument is omitted the empty string is returned.
   * <characters> may contain any number of different characters.  If you 
     want to include the space character, enclose it in double quotes.
   * If the first character in <characters> is the tilde ("^"), then the
     sense of <characters> is negated; <characters> includes all characters
     that are NOT after the tilde.
   * Counting begins after the first space after <characters>.  If multiple
     spaces seperate <characters> and <text>, only the first such space is 
     the seperator; further spaces are part of <text> for the purpose of 
     counting.
   * The return value is the number of initial characters in <text> that 
     preceed the LAST INSTANCE of any characters specified by <characters>.
     That is, it is the position of the last instance of any character in
     <characters> in the string <text>
   * If none of the characters in <characters> appears in <text> (a failed
     search), then -1 is returned.

Practical:
   It used to be common to use $rindex() to find a character in a string so
   that you could extract the parts of the string before and after the 
   character.  This is more easily done by $before() and $after() though.

Returns:
     -1   no character in <characters> was found in <text>
   > -1   index to last instance of something in <characters> in <text>

History
   This function originally appeared in ircII.

Examples:
   $rindex(abc hello there bob)         returns 14
   $rindex(abc   hello there bob)       returns 16
		(because of the spaces after 'c' and before 'h')
   $rindex(xyz hello there bob)         returns -1
   $rindex()				returns the empty string

