The existing "$substr" function takes a string field and two numbers, position and length and it will give you the substring of that field starting at position and of specified length.
What if I could use "$project" phase to figure out the first location of the separator? I could then use "$substr" and I'd be all set. Sure, it's only going to handle finding first occurrence of such character, but it's something.
This particular question was about ignoring the first part of the machine name - i.e. everything up to the first '.' character.
Imagine we have a collection which has these documents, including the name of some machine hostname and we want to report on the domain only, that is, remove the part up to the first '.' character.
We now use the first array element to get the appropriate substring, and here are our results: