I would like to skim through my show run command, and grep out only the "interface" and whether "bpduguard enabled" on that interface. Something like:
sh run | incl (interface | bpduguard)
It works because the second pipe is taken as an alternation character (i.e. "OR") so what happens is that for each line in the config the parser searches for either "interface" or "bpduguard" and prints out a match if it finds either one.
See the chapter "Using the IOS CLI" in the configuration fundamentals book:
It also works for multiple pipes, e.g. "show run | include interface | duplex | speed"