sort them based on creation time.

...

map { [ stat("$sp_dir/$_")->ctime, $_] }

ctime is NOT the creation time of a file.   On Unix and Linix file systems the creation time of the file is NOT stored anywhere.

As the stat function says:

                10 ctime    inode change time in seconds since the epoch (*)

               (*) Not all fields are supported on all filesystem types. Notably, the ctime field is non-portable.  In particular, you cannot expect it to be a "creation time", see "Files and Filesystems" in perlport for details.