I tracked the problem down
Spreadsheet::WriteExcel uses
Spreadsheet::WriteExcel::Workbook which uses
Spreadsheet::WriteExcel::Worksheet which uses
Spreadsheet::WriteExcel::Formula which uses
Parse::RecDescent

and confirmed that Parse::RecDecent duplicates STDERR to 3 filehandles.

This fixes the problem I have.
close Parse::RecDecent::ERROR;
close Parse::RecDecent::TRACECONTEXT;
close Parse::RecDecent::CONTEXT;

Is there any way to track down open filehandles in perl?

In reply to Re^3: Parent waiting on child when using modules by Keystroke
in thread Parent waiting on child when using modules by Keystroke

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