Url redirect to another page on the same site

Question

Basically I want to redirect all requests to my domain to a specific page. For example, redirect all requests to page X, unless you are already on page X, in which case you should just load it. But my solutions just create an infinite loop :/

because 'new users'cant post hyperlinks, assume $LINK = 'http://www.example.com/'

I tried...

RewriteCond %{REQUEST_URI} !=/underconstruction.html
RewriteRule ^(.*)$ $LINK$1 [L,R=301]

RewriteCond %{REQUEST_FILENAME} !^/underconstruction.html
RewriteRule ^(.*)$ $LINK$1 [L,R=301]