Creating port groups on a vSphere Distributed Switch with PowerCLI

I have a large number of new port groups that I want to create on an existing vSphere Distributed Switch.  They will mostly have the same settings with only a few differences.   How can I automate this with PowerCLI?  I'd like to specify the name of an existing distributed switch, then have the script list the port groups that I'm going to add.

Thanks!