$ cat > child
#!/usr/bin/perl
print("child\n");

$ chmod a=rwx,u+s child

$ ls -l child
-rwsrwxrwx 1 ikegami group 34 2008-12-13 10:39 child

$ perl -T -e'%ENV=(); system("./child") and die("error: $?")'
Setuid/gid script is writable by world.
error: 6400 at -e line 1.

$ perl -e'%ENV=(); system("./child") and die("error: $?")'
Setuid/gid script is writable by world.
error: 6400 at -e line 1.