input: Write a function to search a user-provided string within a given list of strings using regular expressions. Return "String matches" if any match is found; otherwise, return "String doesn't match".
  assert search_strings("First second Third", ["First", "Second", "Third"]) == "String matches"
  assert search_strings("Fourth Fifth Sixth", ["First", "Second", "Third"]) == "String doesn't match"
  assert search_strings(" ", ["First", "Second", "Third"]) == "String doesn't match"
  assert search_strings("Second", ["First", "Second", "Third"]) == "String matches"
  assert search_strings("", ["First", "Second", "Third"]) == "String doesn't match"
output: import re
  
  def search_strings(user_string, string_list):
      for pattern in string_list:
          if re.search(pattern, user_string):
              return "String matches"
      return "String doesn't match"