use won't work here. Look at require (and import). By using something like the following, you can import modules and call functions in them on demand:

    ...
    if ($device =~ /^(Device1|Device2)$/){
            require "$device.pm";
            $device->import(); # import the device subroutines here
    }
    ...

# This assumes all devices have and export the same subroutine names
device_function_1();
device_function_2();
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Update: Fixed typo in regex, thanks to Perlbotics