Using euca2ools with HPCloud is simple. You just have to define environment variables containing your credentials and EC2_URL. Here's how: 

export EC2_ACCESS_KEY=TENANT-ID:ACCESS-KEY-ID
export EC2_SECRET_KEY=SECRET-KEY
export EC2_URL=https://az-1.region-a.geo-1.ec2-compute.hpcloudsvc.com/services/Cloud
 
# Or, if you are in AZ-2
export EC2_URL=https://az-2.region-a.geo-1.ec2-compute.hpcloudsvc.com/services/Cloud
 
# Then test
euca-describe-regions
It is important to note that EC2_ACCESS_KEY is a combination of your Tenant ID and Access Key ID (separated by a colon) which can be found in your Account Tab.