Fix issue with execution of perl due to gsub not matching across newlines

Author: marcwickenden

modules/exploits/unix/smtp/exim4_string_format.rb

@@ -322,7 +322,7 @@ def exploit
         buff << res if res
       end
 
-      perl_path = buff.gsub(token, "").gsub(/\/perl.*/, "/perl").strip
+      perl_path = buff.gsub(token, "").gsub(/\/perl.*/m, "/perl").strip
       print_status("Using Perl interpreter at #{perl_path}...")
 
       temp_conf = "/var/tmp/" + Rex::Text.rand_text_alpha(8)