There seems to be precious little further info on that var

Well, it's in in the perlvar manual page in my install ;-)

But it looks like one has to use English to see its default value: 

qwurx [shmem]  ~/perlmonks > perl5.10.0 -le 'print ${^RE_TRIE_MAXBUF}'

qwurx [shmem]  ~/perlmonks > perl5.10.0 -MEnglish -le 'print ${^RE_TRI
+E_MAXBUF}'
65536

[download]

But yes, the number 2**16 rings a bell. It looks like the TRIE-optimization has that limit (of tokens? objects? branches?). Running with -D512 reveals

13104 probes: 

EXECUTING...

Trying 13104 probes with perl 5.010000 at 669148.pl line 18.
1203590260 at 669148.pl line 20.
Compiling REx "TATGTTTCGT|CCGCTTTTTA|CGAAGATTTC|GAACGACGGC|TGTGTTTAAC|
+CCTCA"...
Final program:
   1: TRIEC-EXACT[ACGT] (65526)
      <TATGTTTCGT> 
      <CCGCTTTTTA> 
      <CGAAGATTTC> 
...
      <AACAGTGAGG> 
      <GAAACTCGCG> 
      <GAGAGATGGA> 
65526: END (0)
stclass AHOCORASICKC-EXACT[ACGT] minlen 10 
Compiling REx "((?-xism:TATGTTTCGT|CCGCTTTTTA|CGAAGATTTC|GAACGACGGC|TG
+TGTTT"...
Final program:
   1: OPEN1 (3)
   3:   TRIEC-EXACT[ACGT] (65529)
        <TATGTTTCGT> 
        <CCGCTTTTTA> 
        <CGAAGATTTC> 
...
        <AACAGTGAGG> 
        <GAAACTCGCG> 
        <GAGAGATGGA> 
65529: CLOSE1 (65531)
65531: END (0)
stclass AHOCORASICKC-EXACT[ACGT] minlen 10 
Matching REx "((?-xism:TATGTTTCGT|CCGCTTTTTA|CGAAGATTTC|GAACGACGGC|TGT
+GTTT"... against "ACTCGAATTCCGAATAGATAGAAGTCTGCTGATAATATCGCGCCGGT
TCTGATGCGCCTC"...
Matching stclass AHOCORASICKC-EXACT[ACGT] against "ACTCGAATTCCGAATAGAT
+AGAAGTCTGCTGATAATATCGCGCCGGTTCTGATGCGCCTC"... (1000000 chars)
   0 <> <ACTCGAATTC>         | Charid:  2 CP:  41 State:    1, word=0 
+- legal
   1 <A> <CTCGAATTCC>        | Charid:  4 CP:  43 State:   52, word=0 
+- legal
   2 <AC> <TCGAATTCCG>       | Charid:  1 CP:  54 State:   ce, word=0 
+- legal
   3 <ACT> <CGAATTCCGA>      | Charid:  4 CP:  43 State:  1a2, word=0 
+- legal
   4 <ACTC> <GAATTCCGAA>     | Charid:  3 CP:  47 State:  1a3, word=0 
+- legal

[download]

13105 probes: 

EXECUTING...

Trying 13105 probes with perl 5.010000 at 669148.pl line 18.
1203590218 at 669148.pl line 20.
Compiling REx "TATGTTTCGT|CCGCTTTTTA|CGAAGATTTC|GAACGACGGC|TGTGTTTAAC|
+CCTCA"...
Final program:
   1: TRIEC-EXACT[ACGT] (65531)
      <TATGTTTCGT> 
      <CCGCTTTTTA> 
      <CGAAGATTTC> 
...
      <GAAACTCGCG> 
      <GAGAGATGGA> 
      <CGCCGAGGAT> 
65531: END (0)
stclass AHOCORASICKC-EXACT[ACGT] minlen 10 
Compiling REx "((?-xism:TATGTTTCGT|CCGCTTTTTA|CGAAGATTTC|GAACGACGGC|TG
+TGTTT"...
Final program:
   1: OPEN1 (3)
   3:   BRANCHJ (11)
   5:     EXACT <TATGTTTCGT> (9)
   9:     LONGJMP (104850)
  11:   BRANCHJ (19)
  13:     EXACT <CCGCTTTTTA> (17)
  17:     LONGJMP (104850)
  19:   BRANCHJ (27)
  21:     EXACT <CGAAGATTTC> (25)
  25:     LONGJMP (104850)
...

[download]

The 65531: END (0) looks - though I don't know at all what it means - just too close to 2**16 ...

--shmem 

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

In reply to Re^3: 5.10.0 regex slowdown by shmem
in thread 5.10.0 regex slowdown by BrowserUk

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