Hi,
I ran your code with a use re "debug"; at the beginning and here is what I got:

Compiling REx `(.*? )'
size 10 first at 5
   1: OPEN1(3)
   3:   MINMOD(4)
   4:   STAR(6)
   5:     SANY(0)
   6:   EXACT < >(8)
   8: CLOSE1(10)
  10: END(0)
floating ` ' at 0..2147483647 (checking floating) anchored(SBOL) impli
+cit minlen 1 
Guessing start of match, REx `(.*? )' against `is this odd or not?'...
Found floating substr ` ' at offset 2...
Guessed: match at offset 0
Matching REx `(.*? )' against `is this odd or not?'
  Setting an EVAL scope, savestack=6
   0 <> <is this odd >    |  1:  OPEN1
   0 <> <is this odd >    |  3:  MINMOD
   0 <> <is this odd >    |  4:  STAR
  Setting an EVAL scope, savestack=6
                           SANY can match 2 times out of 2...
   2 <is> < this odd >    |  6:    EXACT < >
   3 <is > <this odd >    |  8:    CLOSE1
   3 <is > <this odd >    | 10:    END
Match successful!
Guessing start of match, REx `(.*? )' against `this odd or not?'...
Not at start...
Match rejected by optimizer
Freeing REx: `(.*? )'
[download]

Looks like it actualy find other matches, but they where refused by the optimizer. The hell if I know why.

By the way, I'm using v5.6.1 on a Debian woody system.