You can always check your perl path and actually see if Error.pm is there so you no if it is installed or not. should be something like c:\perl\lib or c:\perl\site\lib then just look for the Error directory to know if you have it. If you are using an activestate build just go to the command prompt and type ppm. this will bring up a new prompt then type 'install Error' and that will get it for you.
My bad...didn't realize that you were using a unix distr...but if anyone else reads this node, this is how you would install it on a win machine with an active state build.