Maybe some troubleshooting tips will help you going:

perl -d: Set a breakpoint ('b <linenumber>' in the debugger) just before the  $history_entry = Nagios::History->create({ %{$_} }); statement, and singlestep ('s' in the debugger) to see what is happening in detail.

dbi profiling: DBI profiling can be 'misused' to see if any queries go to the database. Read the DBI::Profile manpage for details, or just do DBI_PROFILE=2 script.pl. This should give you some output on the queries that are done to the database.