Apple Script: when moving a file into a folder, is it possible to move duplicates inside that folder? - directory

Question

I have an apple script which moves all files within a folder into a new folder according to the first 6 characters of the filenames.
If the folder already exists, the files get moved into that existing folder instead.
If the file already exists in the new/existing folder, the file to be moved into the folder gets a "copy" extension to the filename – which is not in the script, it's a system function ;-)
My question:
Is it possible to move all existing (duplicate) files into a subfolder (named "_alt" for example), before the other files get moved within the folder (to prevent the "copy"-extension)? I would like to keep both files, the original files and the newly moved files.
Thanks.
This is my existing script:
set mgFilesFolder to (choose folder with prompt "Choose folder…")
(* get the files of the mgFilesFolder folder *)
tell application "Finder" to set fileList to files of mgFilesFolder
(* iterate over every file *)
repeat with i from 1 to number of items in fileList
set this_item to item i of fileList
set this_file_Name to name of this_item as string
set thisFileCode to characters 1 thru 6 of this_file_Name as text
log thisFileCode
tell application "Finder"
try
set nf to make new folder at mgFilesFolder with properties {name:thisFileCode}
end try
end tell
end repeat
set sourceFolder to mgFilesFolder
set destinationFolder to mgFilesFolder
tell application "Finder"
set the_files to (get files of mgFilesFolder)
repeat with this_file in the_files
set the_name to name of this_file
set the_short_name to items 1 thru 6 of the_name as string
if exists folder the_short_name of mgFilesFolder then move this_file to folder the_short_name of mgFilesFolder
end repeat
end tell