I didn't get very far with that. However, I did poke more, and discovered a partial solution. With the code below, Perl opens a window briefly (longer than I would like), then minimizes it, which gets me the faster execution time I'm looking for, but leaves it a pain for the user as a maximized window is opened for several seconds... The code is (fragments copied here)
use Win32::OLE;
use Win32::OLE::Const 'Microsoft Excel';
my $application = Win32::OLE->new("Excel.Application");
my $workbook = $application->Workbooks->Open($pinout);
$application->{WindowState} = xlMinimized;
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