I'm getting -1 on all platforms and perl versions I tried:

perl -le 'system "no-such-program"; print "$? $^O $]"'
[download]

Results:

• -1 hpux 5.006001
• -1 solaris 5.008008
• -1 dec_osf 5.006001
• -1 linux 5.006001
• -1 linux 5.008008
• -1 linux 5.010000