I've seen a lot of mentions of the Perry Poke can you briefly describe the technique and use?
You might be better off doing a google search, especially on videos. In brief a poke cast is a spey cast where the anchor is placed (re-placed may be a better way to describe it) by “dumping” the line instead of casting it. For example you could start any spey cast you like and instead of getting a nice anchor placement you could just do the steps (perhaps even sloppily) and then instead of casting on the forward stroke just lower (dump) your head without shooting any line. The resulting anchor form depends on many factors including how long the head is, why you are doing a poke, and where you are placing the anchor, but the resulting anchor after the poke may be a smooth loop, or just resemble a sinking “ knitting pile” all bunched up in one place. That is absolutely fine as either way, the idea is that when you subsequently sweep the rod back again the water tension on the line together with the dynamics of throwing the D loop back will load the rod, all while straightening the anchor in the water. Think of it as a different way to arrive at the key position before the power stroke.
My understanding has always been, though it might be just me, that the “Perry” poke usually refers to doing a poke out of a single spey, but you can do a poke out of any spey cast, and there are even a few ways to do the dump that don’t exactly resemble any regular spey cast. There are even pokes like doing a dump out straight after a snake roll to set up and overhead cast with a change of direction - this can also be done without landing the line on the water at all, in which case it is arguably not a poke at all. Still it has some features of a poke. Lots and lots of variations are possible, going way beyond poking out of a single spey.
Some people genuinely like doing a poke as an alternative
to a regular spey cast, and find it easier to get a nice 180 layout and a consistent forward cast than a “standard” spey cast. Sometimes they like to substitute them for that one cast they haven’t got the hang of yet.
You can do a poke after/during a messed up cast - when you realize your cast is going to suck just dump the line instead of casting it, then follow up with a beautiful poke. Make sure everyone knows you “meant” to do it that way all along.
When you have little or no room behind you can poke/dump the anchor way out in front of you in such a way as to make a D-loop that also ends further out, thus avoiding the obstacles behind. In this case you are constructing a useful cast that is difficult or impossible to do just by blindly trying to execute a “regular” spey cast in that situation.
There are many ways to do the dump, and there are many spey casters that make it look highly artful and amazing. You can of course even poke out of a poke (re-poke?) repeatedly until you get the anchor where you need it. It ain’t pretty in that case but when you are desperate you will not mind.
There are probably too many poke cast solutions to fishing problems to discuss in one place, but those are the bare bones basics.