Lexer patch question

I am confused why the following change Tom made to scan.l works.
Isn't that 'x' required so xqescape doesn't match '\x'?

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: scan.l
===================================================================
RCS file: /cvsroot/pgsql/src/backend/parser/scan.l,v
retrieving revision 1.123
retrieving revision 1.124
diff -c -c -r1.123 -r1.124
*** scan.l    2 Jun 2005 01:23:08 -0000    1.123
--- scan.l    2 Jun 2005 17:45:17 -0000    1.124
***************
*** 193,199 ****
  xqstart            {quote}
  xqdouble        {quote}{quote}
  xqinside        [^\\']+
! xqescape        [\\][^0-7x]
  xqoctesc        [\\][0-7]{1,3}
  xqhexesc        [\\]x[0-9A-Fa-f]{1,2}

--- 193,199 ----
  xqstart            {quote}
  xqdouble        {quote}{quote}
  xqinside        [^\\']+
! xqescape        [\\][^0-7]
  xqoctesc        [\\][0-7]{1,3}
  xqhexesc        [\\]x[0-9A-Fa-f]{1,2}