928/zoid/0$ perl -le 'print "($1) " while "this_is_broken_" =~ /(.*?)_/gs'
(this)
929/zoid/0$ perl -mre=debug -le 'print "($1) " while "this_is_broken_" =~ /(.*?)_/gs'
Freeing REx: `,'
Compiling REx `(.*?)_'
size 10 first at 5
   1: OPEN1(3)
   3:   MINMOD(4)
   4:   STAR(6)
   5:     SANY(0)
   6: CLOSE1(8)
   8: EXACT <_>(10)
  10: END(0)
floating `_' at 0..2147483647 (checking floating) anchored(SBOL) implicit minlen 1
Guessing start of match, REx `(.*?)_' against `this_is_broken_'...
Found floating substr `_' at offset 4...
Guessed: match at offset 0
Matching REx `(.*?)_' against `this_is_broken_'
  Setting an EVAL scope, savestack=9
   0 <> <this_is_brok>    |  1:  OPEN1
   0 <> <this_is_brok>    |  3:  MINMOD
   0 <> <this_is_brok>    |  4:  STAR
  Setting an EVAL scope, savestack=9
   0 <> <this_is_brok>    |  6:    CLOSE1
   0 <> <this_is_brok>    |  8:    EXACT <_>
                              failed...
                           SANY can match 1 times out of 1...
   1 <t> <his_is_brok>    |  6:    CLOSE1
   1 <t> <his_is_brok>    |  8:    EXACT <_>
                              failed...
                           SANY can match 1 times out of 1...
   2 <th> <is_is_brok>    |  6:    CLOSE1
   2 <th> <is_is_brok>    |  8:    EXACT <_>
                              failed...
                           SANY can match 1 times out of 1...
   3 <thi> <s_is_brok>    |  6:    CLOSE1
   3 <thi> <s_is_brok>    |  8:    EXACT <_>
                              failed...
                           SANY can match 1 times out of 1...
   4 <this> <_is_brok>    |  6:    CLOSE1
   4 <this> <_is_brok>    |  8:    EXACT <_>
   5 <this_> <is_brok>    | 10:    END
Match successful!
(this)
Guessing start of match, REx `(.*?)_' against `is_broken_'...
Not at start...
Match rejected by optimizer
Freeing REx: `(.*?)_'
930/zoid/0$ perl -v

This is perl, v5.6.1 built for i386-linux