A very last idea: I never used perl on Winows, but I have had some bad experiences using Word via OLE2 from Borland Delphi.

I remember having had timing problems in a similar context: tell word to open a file, do things (mainly macro) , save, and close, and then if you try to open the file just saved it is locked! Never worked out exactly the cause, but it was avoided inserting a delay after closing Word and before attempting to open the saved file

Try a sleep before the call to get_file...