First off, definitely take a look at this page: http://communities.vmware.com/community/developer/forums/vsphere_sdk_perl at the Resources section on the right.
This is a great document showing you the details of how the perl toolkit no redubbed vSphere SDK for Perl, definitely worthwhile to go through the documentation:
If you're familiar with the esxcfg-* commands, then you'll notice as part of the vCLI/RCLI which utilizes the vSphere SDK for Perl has the same exact command set but setup to help do remote management:
There are some additional utilities that come bundled with the vCLI/RCLI as well, take a look here for the list:
As you know, these are all Perl scripts, meaning you can open them up and see how it's implemented and how they use the vSphere API, the reference doc for the API is also very important too:
I think the easiest way to learn this is to start playing with some of the canned scripts and to make it even easier to have an environment that's all setup for you with both the vCLI and vSphere SDK for Perl, you can download the vMA which is a VMware management assistant appliance for remotely managing your ESX(i) and vCenter systems.
The version of Perl that's being used is actually 1.6 but the naming of vCLI is 4.0 which is in conjunction with vSphere 4.0 release, it has nothing to do with the version of Perl (yes the naming/numbering really sucks and confuses a lot of people)
Here is a nice document that does the breakdown of all the various APIs/SDKs/etc. : Getting Started with vSphere SDKs - Updated for SDK 4.1 release
VIX is primary for guest management, it's to be used or can be used in conjunction with the vSphere API's and you can find more information on the VIX page.
Also here is some sample code for vSphere SDK for Perl: http://communities.vmware.com/community/developer/codecentral/vsphere_perl and vGhetto Script Repository
Well, I'm sure this is a handful of information and it'll take some time to digest, but again the best way to learn is to start to play with it and you'll get a hang for it.
Good luck and happy scripting
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
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er - wow - that's just what I needed.
A little reading to catch up on though - but loads clearer!