The Execute bit on a Directory determines whether you can list the
contents of that directory.

The Execute bit on a File determines whether a shell will allow you to
"run" the contents of the file.  Note that you may still be able to run a
program whose execute bit is not set:

   $ ls -l
   total 4
   -rw-r--r--    1  Dec 16 09:49 myprogram.pl
   $ ./myprogram.pl
   bash: ./myprogram.pl: Permission denied
   $ perl myprogram.pl
   Hello, world!
   $

The shell won't execute the myprogram.pl file, but Perl can read it and
execute it.

   $ chmod u+x myprogram.pl
   $ ./myprogram.pl
   Hello, world!

Now the shell will also let you execute it.

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