I think you'll have better luck if you only load DBI in the child.

my $pid = fork();
if (not defined $pid) {
   # Fork error
   ...
}
elsif (not $pid) {
   # Child process
   require DBI;  # Not "use" to load in child only.
   ...
}
else {
   # Parent process
   ...
}
[download]

This is based on a vague memory of something I once read. I hope it works.