You may create singleton methods like so:

foo = MyThing.new

def foo.do_stuff
  "code"
end

But I cannot seem to grock the syntax that would allow me to name the
method from a variable. Such as:

foo = MyThing.new
bar = "do_stuff"
def foo.%{#{bar}} #This is totally wrong I think. 
  "code"
end

Any suggestions? I'm starting to get a spinning head. :)

To be clear, I want to create a singleton method on the instance of
MyThing, not add the method to the MyThing class.

This is mentioned here:

http://www.rubyist.net/~slagell/ruby/singletonmethods.html

but I'd like to do it dynamically.

Many thanks!

-L