If //c does that, I would call it a bug. Can you show a short test case? In at least this simple case, the flag (called MINMATCH, i.e. a minimum length of 1 will be required on the next match) is set: 
$ perl -we'use Devel::Peek; ($x="abc")=~/.??/gc; Dump $x'
SV = PVMG(0x10183f00) at 0x10167ca4
  REFCNT = 1
  FLAGS = (SMG,POK,pPOK)
  IV = 0
  NV = 0
  PV = 0x10142828 "abc"\0
  CUR = 3
  LEN = 4
  MAGIC = 0x10147380
    MG_VIRTUAL = &PL_vtbl_mglob
    MG_TYPE = PERL_MAGIC_regex_global(g)
    MG_FLAGS = 0x01
      MINMATCH

[download]
(Note that older perls have a bug where Devel::Peek doesn't correctly show the flag by name, but you can still see the bit in MG_FLAGS.)

In reply to Re^3: zero-length match increments pos() by ysth
in thread zero-length match increments pos() by Errto

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