While this method works, it is a bit slow, since it checks for the existence of 'bar' EVERY character. Use the "unrolling the loop" technique, as found in "Mastering Regular Expressions":

Update: tilly's right, mine fails to match on a specific type of string ("foobabfoo"). Fixed below. 
m{
  foo
  (             # save to $1
    [^b]*       # 0 or more non-b characters
    (?:
      b+        # 1 or more b's
      (?:
        a(?!r)  # an 'a' NOT followed by an 'r'
        |       # or
        [^a]    # a non-a character
      )
      [^b]*     # 0 or more non-b characters
    )*          # that whole b... subset, 0 or more times
  )
  foo           # and foo
}x;

[download]
The general pattern behind unrolling the loop is to get your regex to look something like OK* ( NOTOK OK* )*.

$_="goto+F.print+chop;\n=yhpaj";F1:eval

In reply to RE: RE (tilly) 2: Regex'ing backreferences by japhy
in thread Regex'ing backreferences by Uruk

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