Is there a good resource on how perps actually work? i.e a technical specification on how to implement them?
BitMEX and Hyperliquid have fairly detailed documentation about how they implement perps and there are probably open source projects out there.
Yes!
If you want to get into the deepest detail there are several decentralised perpetual futures exchanges.
Here are some open source codebases on Github:
https://github.com/vegaprotocol/vega
https://github.com/dydxprotocol/v4-chain/
https://github.com/gmx-io/gmx-synthetics
https://github.com/0xOstium/smart-contracts-public/
Vega is a stalled project, but they have good documentation:
https://docs.vega.xyz/release/concepts/new-to-vega