DB<3> use re "debug"; print 'abcdc' =~ /(.).*\1/
Compiling REx "(.).*\1"
Final program:
   1: OPEN1 (3)
   3:   REG_ANY (4)
   4: CLOSE1 (6)
   6: STAR (8)
   7:   REG_ANY (0)
   8: REF1 (10)
  10: END (0)
minlen 1
Matching REx "(.).*\1" against "abcdc"
   0 <> <abcdc>              |   0| 1:OPEN1(3)
   0 <> <abcdc>              |   0| 3:REG_ANY(4)
   1 <a> <bcdc>              |   0| 4:CLOSE1(6)
   1 <a> <bcdc>              |   0| 6:STAR(8)
                             |   0| REG_ANY can match 4 times out of 2147483647...
   5 <abcdc> <>              |   1|  8:REF1: "a"(10)
                             |   1|  failed...
   4 <abcd> <c>              |   1|  8:REF1: "a"(10)
                             |   1|  failed...
   3 <abc> <dc>              |   1|  8:REF1: "a"(10)
                             |   1|  failed...
   2 <ab> <cdc>              |   1|  8:REF1: "a"(10)
                             |   1|  failed...
   1 <a> <bcdc>              |   1|  8:REF1: "a"(10)
                             |   1|  failed...
                             |   0| failed...
   1 <a> <bcdc>              |   0| 1:OPEN1(3)
   1 <a> <bcdc>              |   0| 3:REG_ANY(4)
   2 <ab> <cdc>              |   0| 4:CLOSE1(6)
   2 <ab> <cdc>              |   0| 6:STAR(8)
                             |   0| REG_ANY can match 3 times out of 2147483647...
   5 <abcdc> <>              |   1|  8:REF1: "b"(10)
                             |   1|  failed...
   4 <abcd> <c>              |   1|  8:REF1: "b"(10)
                             |   1|  failed...
   3 <abc> <dc>              |   1|  8:REF1: "b"(10)
                             |   1|  failed...
   2 <ab> <cdc>              |   1|  8:REF1: "b"(10)
                             |   1|  failed...
                             |   0| failed...
   2 <ab> <cdc>              |   0| 1:OPEN1(3)
   2 <ab> <cdc>              |   0| 3:REG_ANY(4)
   3 <abc> <dc>              |   0| 4:CLOSE1(6)
   3 <abc> <dc>              |   0| 6:STAR(8)
                             |   0| REG_ANY can match 2 times out of 2147483647...
   5 <abcdc> <>              |   1|  8:REF1: "c"(10)
                             |   1|  failed...
   4 <abcd> <c>              |   1|  8:REF1: "c"(10)
   5 <abcdc> <>              |   1|  10:END(0)
Match successful!
cFreeing REx: "(.).*\1"

  DB<4>