lua, split string

This is almost embarrassing to ask about but I'm stuck. I'm trying to split a string at whitespace. I'm broadly assuming that string.gmatch() returns an array, which it appears to do in the loop example below. However if I try and grab an element from the return value it throws up an error, telling me it's a function. Can anyone help:?

local example = "an example string"

-- works as expected.
 for i in string.gmatch(example, "%S+") do
  Debug.logn(i)
end

-- tells me s is a function
Debug.logn( string.gmatch( example, "%S+" ) )

-- tells me I'm trying to index a function value
Debug.logn( s[1] )