What is the **regex** in `.htaccess` to go from those urls: 

```
example.com/hello-world-world
example.com/hello-world-hello

```

to this one:

```
example.com/hello-world

```

using RewriteCond like this:

```
RewriteCond %{REQUEST_METHOD}  !=POST
RewriteCond %{REQUEST_URI} ^REGEX$
RewriteRule . %1 [R=301,L]

```