You will find Lotus documentation on the 123 file format here

You can extract and convert the binary information that you need using unpack. Since the binary records have defined lengths it should be easy to iterate through the file record by record looking for salient information.

Other functions that you might find useful in this task are pack, seek, tell and binmode.

The file format is actually quite similar to the Excel file format so you may be able to get some ideas from Spreadsheet::ParseExcel.

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John.