then I'm going to complain when .xls needs more :)

MS-Excel itself probably needs that much

I've used Spreadsheet::ParseExcel::Stream instead of Spreadsheet::ParseExcel and it uses 1.0GB memory after parsing an xls-file with a single worksheet and 64772 rows and 120 columns. This is before I go through the parsed worksheets and rows.
Opening this in Excel (2007) seems to use only 230MB.
So even with this module, reading a somewhat large Excel file uses excessively large amounts of memory. Edit: The xls-file is 122MB.

print("Before creating new Spreadsheet::ParseExcel::Stream:\n" . `free
+ -m`);
    my $ExcelParser = Spreadsheet::ParseExcel::Stream->new($FileName);
print("After creating new Spreadsheet::ParseExcel::Stream:\n" . `free 
+-m`);
[download]

results in

Before creating new Spreadsheet::ParseExcel::Stream:
             total       used       free     shared    buffers     cac
+hed
Mem:          3011       1250       1761          0          2        
+177
-/+ buffers/cache:       1071       1940
Swap:          956        177        779
After creating new Spreadsheet::ParseExcel::Stream:
             total       used       free     shared    buffers     cac
+hed
Mem:          3011       2257        753          0          2        
+177
-/+ buffers/cache:       2077        933
Swap:          956        177        779
[download]

... it uses 1.0GB memory after parsing an xls-file with a single worksheet and 64772 rows and 120 columns.

Yes, the claim of "no memory overhead" is a bit of a mistake/exaggeration. But you would get the same result using just Spreadsheet::ParseExcel with the CellHandler and NotSetCell options (which S::PE correctly says "reduces" memory overhead, not has "no" memory overhead). Spreadsheet::ParseExcel parses and saves a bunch of stuff before it even gets to the cell data. So the S::PE with the CellHandler/NotSetCells options and/or S::PE::Stream only save you from storing the cell data in memory. I don't know if it would be possible to tell S::PE to not save the metadata before the cell data (or possible to modify it to implement such a thing). Only jmcnamara would know for sure..

Spreadsheet::ParseExcel::Stream uses Coro, that stuff could be buggy (or being used buggily)