If you mean all the progress messages are appearing all at once at the end, that is because you are not using

$mw->update;
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throw that into the processing loop after you do your ->Insert or whatever you are using to post the messages and they will appear one at a time ($mw being the main window handle).

This is analogous to flushing output to a file stream, etc, etc, when it builds up in a buffer. You cannot set it "unbuffered", but you can do a flush using ->update. You do not need to get into threading or forking just for this.