You can use the `expansions` block in your .rpo to replace content with a value computed through executing a custom [starscript](https://github.com/MeteorDevelopment/starscript/wiki).
All values are available in starscript like this: `<pack id>.<entry>`
The expansions block contains a key ("lights") and a script, which is executed when the file is loaded. All instances of the key (formatted as ${name} -> ${lights} in this example) will be replaced by the result of the script. Make sure to only use this feature on text files as unexpected results my occur otherwise