c:\perl\excel\TestRead.pl "c:\test.xls"
Wild guess. Could \t be perchance translated to a tab, leading your script to open c:\   est.xls
Try  my $file = "c:\test.xls" in your snippet, and you should get something like this:

P:\>c:\temp\openxl.pl "c:\temp\test.xls"
OLE exception from "Microsoft Office Excel":

'c:     emp     est.xls' could not be found. Check the spelling of the
+ file name,
and verify that the file location is correct.

If you are trying to open the file from your list of most recently use
+d
files on the File menu, make sure that the file has not been renamed, 
+moved,
or deleted.

Win32::OLE(0.1702) error 0x800a03ec
    in METHOD/PROPERTYGET "Open" at c:\temp\openxl.pl line 10
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