Which elements of -syntax- retain their quotes?

[matthew-white]

This one actually comes up a lot: new programmers get confused about this.

syntax automatically strips quotes from string options. For instance, for this program:

program say
    syntax, this(string)

    display "`this'"
end

the following two commands result in the same output:

say, this("Hello world")
say, this(Hello world)

However, syntax does not strip quotes from string asis options. Further, for syntax anything, it does not strip quotes from anything'`: anything' is like ``0' in this way.