This was originally a correction note, then I realized that I could just edit the original post to be correct, so I did. I don't see a way to delete this post entirely (short of marking it for consideration, which would be making my mistake into more people's problems), so here's what it was.

---- original content ---

oops,

die "no blank lines" 
  unless ($first_blank > 0)
[download]

should have been:

die "no blank lines" 
  unless ($first_blank >= 0)
[download]