My question was ... is there is a way to pack these into just a few parameters, and unpack them ... to get the full list back.

Sounds like you have some input as to how the parameters are passed to your program.

If the combined length is (or becomes) an issue (the number doesn't matter, it's the total of bytes that is limited), you might consider having the "caller" of your program pipe the parameters to your program's standard input (STDIN), one parameter per line.

If a lot of the parameters are numbers, having the caller pack, then uuencode the parameters might compact the total number of bytes being passed, but this will add processing overhead.

If that isn't enough, the caller could compress the parameters using bzip, gzip or similar, then uuencode that. But that will add even more processing overhead.

The simplest, least overhead, way to get around command line limits would be to pipe the parameters, as I described.