> perl -e'use re 'debug'; qr/(x{100}.*y{100})*/' 
Compiling REx "(x{100}.*y{100})*"
Final program:
   1: CURLYX[0] {0,32767} (18)
   3:   OPEN1 (5)
   5:     CURLY {100,100} (9)
   7:       EXACT <x> (0)
   9:     STAR (11)
  10:       REG_ANY (0)
  11:     CURLY {100,100} (15)
  13:       EXACT <y> (0)
  15:   CLOSE1 (17)
  17: WHILEM[1/1] (0)
  18: NOTHING (19)
  19: END (0)
minlen 0 
Freeing REx: "(x{100}.*y{100})*"