nph>perl -Mre=debug -ne'/^(?:CP|K[LM]|ME|P[AM]|S[LZ]|WX|YZ)XX1/;print">"'
Freeing REx: `","'
Compiling REx `^(?:CP|K[LM]|ME|P[AM]|S[LZ]|WX|YZ)XX1'
size 59 Got 476 bytes for offset annotations.
first at 2
   1: BOL(2)
   2: BRANCH(5)
   3:   EXACT <CP>(57)
   5: BRANCH(19)
   6:   EXACT <K>(8)
   8:   ANYOF[LM](57)
  19: BRANCH(22)
  20:   EXACT <ME>(57)
  22: BRANCH(36)
  23:   EXACT <P>(25)
  25:   ANYOF[AM](57)
  36: BRANCH(50)
  37:   EXACT <S>(39)
  39:   ANYOF[LZ](57)
  50: BRANCH(53)
  51:   EXACT <WX>(57)
  53: BRANCH(56)
  54:   EXACT <YZ>(57)
  56: TAIL(57)
  57: EXACT <XX1>(59)
  59: END(0)
anchored `XX1' at 2 (checking anchored) anchored(BOL) minlen 5
Offsets: [59]
        1[1] 4[1] 5[2] 0[0] 7[1] 8[1] 0[0] 9[4] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 13[1] 14[2] 0[0] 16[1] 17[1] 0[0] 18[4] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 22[1] 23[1] 0[0] 24[4] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 28[1] 29[2] 0[0] 31[1] 32[2] 0[0] 33[0] 35[3] 0[0] 38[0]

>SLXC1
Guessing start of match, REx `^(?:CP|K[LM]|ME|P[AM]|S[LZ]|WX|YZ)XX1' against `SLXC1
'...
String not equal...
Match rejected by optimizer
>