How much of your C# code do you understand?

Reading your code, there is the line:

MemoryMappedFile.CreateOrOpen("Test", 1000, MemoryMappedFileAccess.Rea
+dWrite);
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This suggests that the code opens or creates a file named Test in the current directory, and as jcb suggests, you could use that as the filename.

If this is your code, maybe you want to use a different approach than a memory mapped file. If this is not your code, consider talking to the original author about using a different serialization scheme, like JSON, or a well-defined binary layout, or just not using a memory mapped file when a plain file will do just as well.

Msdn docet MemoryMappedFile.CreateOrOpen Metod: Creates a new empty memory-mapped file or opens an existing one IF one with the same name exists. (i assure not exist a file in my HDD with name Test ) if i wanted to open a file i would used this MemoryMappedFile.CreateFromFile Create a memory-mapped file from a disk file.

If you don't create the file on disk, how do you expect Perl to read from that file?

My suggestion to you is to look at other approaches of passing data to another program than using an unnamed memory mapped file.

Your C# code appears to be creating a file named "Test" in its current directory. You will want perl to open that file.

Note that synchronization between memory-mapped files and the rest of the filesystem API is usually unspecified until msync() or its equivalent is called or the file is unmapped, so your data may not be actually written to the file until your C# program exits or performs some kind of synchronization call.