"What's the recommended way to receive HTTP input on multiple channels, while abstracting away which channel(s) was used?" is, itself, a perfectly good question.

I have no idea why you're so hellbent on painting this as an XY problem. The OP needs to receive input. The OP is used to receiving it via CGI.pm. The OP understands that CGI.pm is deprecated and wants to know the current, non-deprecated alternative which comes closest to working in the same way.

None of that is application-dependent, nor does it suggest that there's a "real question" behind the question of "how do I accept user input?".