Strange.  32-bit Perl running on Linux (SuSE 10.2) x86_64:

$ ./669148.pl -s 668954.p10 -S=1e6 -N=13104 | wc -l
Trying 1000 probes with perl 5.010000 at ./669148.pl line 18.
1203556433 at ./669148.pl line 20.
1203556436 at ./669148.pl line 27.
28418
$ ./669148.pl -s 668954.p10 -S=1e6 -N=13105 | wc -l
Trying 1000 probes with perl 5.010000 at ./669148.pl line 18.
1203556454 at ./669148.pl line 20.
1203556457 at ./669148.pl line 27.
28418
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(Printing ${^RE_TRIE_MAXBUF} shows nothing)

Update: Ahh, the passing of the params didn't work... (I overlooked the 1000 in the output). When fixing this, I can actually reproduce the problem. Sorry for the noise.