For anyone else searching, what I ended up doing was a little more simple. Looking into forking and threading was intimidating, since I'd need variables to be passed between the two and didn't understand how that worked.

Since both standard select() and File::Tail::select have timeouts, I loaded STDIN and the File::Tail object in the appropriate one, and read from each inside a loop. Kinda silly how simple that seems to me now.

I was initially concerned about performance when doing so, but then I guess all that each select method is doing is reading in a timed loop anyway. My method seems to be working great. Thank you to those who provided input.