In theory, you should be able to pass the filehandle in and there are tests for that.

That fails too. Tested by changing

my ($fh, $fn) = tempfile();
my $db = DBM::Deep->new( $fn );
[download]

to

my $fh = tempfile();
my $db = DBM::Deep->new( { fh => $fh } );
[download]

in the test I provided earlier.