Make certain you're dumping a single value. This is because do is evaluating the file and returning the last thing evaluated, which in the case of a single dumped hashref should be the hashref itself e.g

shell> perl -MData::Dumper -e 'my %h = qw/foo bar baz quux/;
                               print Dumper \%h' > h.dump
shell> cat h.dump
$VAR1 = {
          'foo' => 'bar',
          'baz' => 'quux'
        };
shell> perl -MData::Dumper -e 'my $h = do "h.dump"; print Dumper $h'
$VAR1 = {
          'foo' => 'bar',
          'baz' => 'quux'
        };
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Note that I'm using a hash ref there, not a hash. You'll also want to turn on $Data::Dumper::Terse if you're running with strict 'vars' as it'll choke on $VAR1.