It appears to me that you're using Win32::OLE. Well, you can get at the sheet itself by specifying an index (apparently: 1-based). One of the properties of a worksheet is, of course, the name.

my $Book = $Excel->Workbooks->Open( $filename );      # open the file
my $sheetcount = $Book->Worksheets->Count;
foreach my $i (1 .. $sheetcount) {
    printf "Sheet #%d: %s\n", $i, $Book->Worksheets($i)->Name;
}
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