I'd suggest Net::DNS over gethostbyaddr.. From the man pages of Net::DNS::Resolver that I was able to locate off Google,
tcp_timeout can be used to set the timeout for queries, the default being 120 sec

After using gethostbyaddr for a reporting/log file analysis tool that I wrote not too long ago, I might even suggest a locally cached copy of addresses.. this made a significant difference in the speed of the app for subsequent invocations..

HTH