This is the first clue you have given that you are running Windows machines.
IF these machines are on the same domain, and/or IF your login credentials on C have access to the shares on A and B, you can do something like this from the command-line on machine C:
C:\> perl \\A\Path\to\code\share\codefilename.pl \\B\path\to\data\Dat
Then your prograam can use the diamond operator to access the file, without being programmed explicitly for file access on a remote machine.
If the machines do not have explicit shares, and if you have administrator priviledges,
You can access the "hidden" shares at the root of the drive like:
Note : C$ indicates the C:\ drive.
I hope life isn't a big joke, because I don't get it.