in reply to Is your Perl broken? Bug help needed.

I'm getting the same thing on my box.

perl 5.6.1 - build from source not rpm - RedHat 7.1
#!/usr/bin/perl while ("this_is_broken_" =~ /(.*?)_/gs) { print "($1) "; }

Here's its debug output.
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!
Guessing start of match, REx `(.*?)_' against `is_broken_'...
Not at start...
Match rejected by optimizer
Freeing REx: `(.*?)_'

Outputs: (this)
#!/usr/bin/perl while ("this_is_broken_" =~ /(.*?)_/g) { print "($1) "; }
Outputs: (this) (is) (broken)

BMaximus