Those variables are only there as examples, theres nothing in the plugin that actually processes them. You need to globally replace them with the correct values when you use the plugin.
The 127 error can be caused by problems with Perl installation and perl module locations.
HOWEVER -
the check_esx3 plugin has been completely re-written to use the official VMware Perl VI API which queries the virtual centre directly (or the esx server) and is more future-proof (and more accurate). It is similar to check_esx3 now but not fully backwards compatible but can do nifty things like stats over a whole cluster, locating a guest stats in the cluster no matter which host it lives on, and so on.
This new check_vmware is available here:
viewtopic.php?f=35&t=1648