String comparison mistake - string

Question

I tried to write a set of functions that check the expiration date for a domain name:
(ql:quickload 'inferior-shell)
(defun whois-lookup (site)
(let ((request (format nil "whois ~a" site)))
(inferior-shell:run/ss request)))
(defun match-expiration-string (input)
(let ((test-string "Registrar Registration Expiration Date:"))
(string> input test-string)))
(defun domain-expiration-date (site)
(with-input-from-string (input (whois-lookup site))
(loop for line = (read-line input nil nil)
while line do
(when (match-expiration-string line)
(format t "~A~%~t~A ~%" site line)))))
I'd call it like this: (domain-expiration-date "startpage.com").
Unfortunately, instead of just displaying the relevant line, it shows all of them.
match-expiration-string seems to be working correctly, so I have no idea what the problem is.
CL-USER> (match-expiration-string "Registrar Registration Expiration Date: 2016-05")
39 (6 bits, #x27, #o47, #b100111)
CL-USER> (match-expiration-string "Registrar Registration Expiration ")
NIL

Answer 1

As suggested by jkiiski, it works with a regular expression:
(defun match-expiration-string (input)
(let ((test-string "Registrar Registration Expiration Date:"))
(ppcre:scan test-string input)))
==>
CL-USER> (domain-expiration-date "startpage.com")
startpage.com
Registrar Registration Expiration Date: 2018-10-10T04:00:00Z
NIL
Like Joshua Taylor says, you don't need regex, only search. I also noticed that "Registrar Registration Expiration Date:" wasn't in every whois response, so I modified the search (and made place in case I needed other search strings for other types of domains):
(defun match-expiration-string (input)
(let ((inclusion-strings '("Expiration Date:"))
(exclusion-strings '("Registrar Registration Expiration Date:")))
(when (some #'(lambda (s) (search s input))
inclusion-strings)
(notany #'(lambda (s) (search s input))
exclusion-strings))))