Is there any reason why you must use an external SNMP query?
NET::SNMP has a good non-blocking SNMP dispatcher which will go all 500+ queries in next to no time, with very little overhead.
Have a quick look at this writeup: Re^3: threads and SNMP Session for an example of how.
Thanks for your quick reply!
Now I am using Solaris SMA (based on free-net-snmp) which is included in Solaris 10 by default. Next step may indeed/probably be to switch to NET::SNMP.
Thanks for info, as I did not know such perl-module did exsist!