cwd() > Returns the current directory of the shell

flag(f) > Checks if the `f` flag has been passed to Hilbish.

read(prompt) -> input? > Read input from the user, using Hilbish's line editor/input reader.
This is a separate instance from the one Hilbish actually uses.
Returns `input`, will be nil if ctrl + d is pressed, or an error occurs (which shouldn't happen)

run(cmd) > Runs `cmd` in Hilbish's sh interpreter