in reply to Perl regular expression rules

You may want to give more details about what you're trying to accomplish, because...

[user@host]$ ll /bin/su -rwsr-xr-x 1 root root 30148 Jul 21 19:54 /bin/su [user@host]$ ln -s /bin/su notsu [user@host]$ ./notsu Password: [root@host]#

So if you're trying to use this to prevent people from running su it's probably not a good idea.