Rake task syntax help

Hi all,

I am currently working on writing a script for a image archive web app
and need a little help.

The script needs to import a load of images, from one of two locations
given by a XML feed. Most of it is sorted, except choosing the
appropriate location of the image. The XML feed simply stores the file
name of the image but not the full path. The image can come from two
locations either "http://www.tistore.co.uk/assets/images/HiRes/#
{product.image}.jpg" (High Resolution) or "http://www.tistore.co.uk/
assets/images/300-200/#{product.image}.gif" (Low Resolution). The
first will be where a high resolution version is available and the
second a low resolution.

There will definitely be a low resolution image however I need the
script to check whether high resolution version is available if so use
it as this is the preferred version if possible.

This is what i've got so far:

@image = Image.new
unless product.image.empty?

if product.image == 'noimage' && 'NOIMAGE'
puts "No Image - SKIP"

[@image.image_file_url = "http://www.tistore.co.uk/assets/images/HiRes/
#{product.image}.jpg"] rescue OpenURI::HTTPError
[@image.image_file_url = "http://www.tistore.co.uk/assets/images/
300-200/#{product.image}.gif"] #this is where the problem lies


The script needs to first check the High resolution location (http://
www.tistore.co.uk/assets/images/300-200/#{product.image}.gif") but if
there is a 404 Not Found error(OpenURI::HTTPError) revert to the low
resolution location (http://www.tistore.co.uk/assets/images/HiRes/#

If anyone has any suggestions on the syntax to achieve this, all help