Neither of the two other solutions are what I'd use on Windows to start a detached process. The ampersand-method doesn't work on Windows, because the interpretation of the ampersand is shell-dependent. I stay away from fork() because it brings many problems with it whenever shared resources are released.

On Windows, you have three methods of launching a process detached from the main program. The easy way is to use the start command of cmd.exe, see help start for more information:

system( "start $File");
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to launch $File detached from your program.

If you want to go to the bare metal, there is the CreateProcess function which you can access via Win32::API to create a process.

If you want to stay close to Perl, you can use

system( 1, $File );
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which is a bit underdocumented and does weird things to your console window, but otherwise also spawns an independent process.