It all depends on what you are doing, and what is happening with the file. The warning from File::Temp points to the fact that after you have opened a file, something else may have (re)moved the file, and created another file with the same name as the original one. I think the remark in File::Copy points out that it's possible a file handle might not be opened with options that are appropriate - in the next sentences, it stresses the importance of having opened the file in "binmode" (on certain platforms).

Abigail