I solved this same situation on an application I wrote to do remote system administration. It allows for the backend to be OS independant by having a set of modules that are written spefically for each OS.

I then load the appropriate modules in a config file and do a

 
eval "require $backend_name_from_config";
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You can see this in action at ftp://ftp.wiles.org/pub/RUM/

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Frank Wiles <frank@wiles.org>
http://frank.wiles.org