Try these:

(let ((x ''foo)) (printf "Matching ~S\n" x)
   (match x ('foo (printf "Found foo\n"))
            (''foo (printf "Found 'foo\n"))))

(let ((x 'foo)) (printf "Matching ~S\n" x)
   (match x ('foo (printf "Found foo\n"))
            (''foo (printf "Found 'foo\n"))))

...the difference purely being in the definition of x