File::Copy will be a native port and will expressed in terms of 'C' calls to the underlying O/S functions. 'C' functions will be called via .DLL's or .so's to do the job without needing a separate processes or programs.

The end result is that Perl can copy or move a file faster than the command line shell (like bash, etc) can do it because there is no bash interpreter! (a separate program that has to get started and there are inefficiencies with that...).

Your result is not surprising and is expected.

A simple Perl program can beat the heck out of MS XCOPY.

Well written Perl runs very quickly.