$ perl -le 'print $c++ for 0..0xFFFF' > test; ls -l test
-rwxr-xr-x 1 user user 382106 2006-11-14 15:04 test

$ perl -e 'open F, "test"; print "$! => $_" while <F>'
Bad file descriptor => 0
Bad file descriptor => 1
Bad file descriptor => 2
...