How to create custom navigation template for a site with anchors on index page.

Hi,

I have a site where the global nav takes you to 3 anchor links on the homepage and the other links go to separate pages.

I know how to create a perch custom template where I can manually add anchor fields, however I still want to mark links as "selected" if that is where the user is.

so if the address bar is www.domain.com/#about-us then the html should be

<li><a href="#about" class="selected">About Us</a></li>

What would be the cleanest way to query the URL and change the class state, also without interupting the usual dynamic elements?

I haven't pasted the full template as I intend to duplicate the standard item.html as a starting point.