Johnathan Palardy wrote an article on integrating REPLs with Vim which has the brilliant idea of using screen's message passing to send snippets from vim to any REPL. There's nothing like planning commands in vim and then automatically sending them to another task, like working with R's REPL, updating a router, or hacking on whatever.

Doing this for a bit quickly leads one to a REPL All The Things! mentality, which has some odd consequences:

1. used to use languages without REPLs, now don't
2. used to edit files remotely via $EDITOR, now use 'ed'
3. now bash is a REPL for building scripts

For me, instead of map'ing new character combos, it's better to set up a user-defined command in vim, so one can pass it a range and some arguments as needed, e.g. screen.vim.