I vote for a key (not a character) to create separators for passing arguments. For example such a key could be the Tab key, the Caps Lock key, a Win key or whatever a user wants. I'm not sure about the internals of FARR but I think the command line of FARR shouldn't be limited to text but objects in general. This means: A command could be made up of a chain (or even a net!?) of objects. Some of them are plain text, others are separator objects etc.. How these objects are created is an other topic (ok, for text it's clear; other possibilities are the special keys or key combinations; system events etc. etc.). Such objects may change the behaviour of the input line completely. For example some parts of the input line may become uneditable (as a little separator arrow) or only changeable within certain limits (as a mini-dropdown menu). They could even change the whole input line while being created... (i would call them transformers) (stay calm... I'm only flushing ideas ;) ) Some of them might become invisible just as they have been typed.
There may be even access rights for these objects such that a certain object may only read the next N entries in the command line.
An object to denote a single string would be nice too (compare the whole string "foo bar" with the single words "foo" and "bar").

To sum up: Just because a launcher is keyboard based it hasn't to be text based!

Perhaps you could use some of the ideas Mouser :P (especially the "key creates separator" would be nice...)

P.S.: "Enter" would just instantiate another object which immediately opens the selected result. There might be other keys for that!  E.g. Shift+Enter for "open result" and "Enter" for "line break".

As you know, the way texts are matched with the help of regular expressions is not necessarily unique!
Perhaps the regexp parsing engine is not greedy enough or too greedy.
@mouser: IMHO it should be set to greedy and it should be possible to set certain parts ungreedy with a "?", for example: "(.+?) (.+)" would try to make the first part of the match as short as possible (until the first space).