Conditional code possible in .vilerc?

[Chris Green]

I run vile on several systems, up until now they have been 'my'
systems where vile is installed in /usr with config files in
/usr/share/vile.

However I have just installed vile on a system (my cPanel hosting
site) where I just have a user account.  I built vile very quickly and
easily to install it in my home directory.  

The (minor) problem is that I have a .vilerc that I share across all
systems that currently does "source /usr/share/vile/filters.rc", this
obviously doesn't work on the new system where it should be "source
~/share/vile/filters.rc".

I'd rather not have a custom .vilerc if I can avoid it, is there any
way to code conditionally in the .vilerc to test where the filters.rc
file is?  Something like:-

    if exists /usr/share/vile/filters.rc
        source /usr/share/vile/filters.rc
    else
        source ~/share/vile/filters.rc
    fi

-- 
Chris Green