Please show the code you are running.

Note that the error message complains about open with a lower case "o".

The Excel method is named Open, with an upper case "O".

    use Win32::OLE qw(in with);
    use Win32::OLE::Const 'Microsoft Excel';
   $Win32::OLE::Warn = 3;      
$excelfile= "C:/perlpractice/FU_HMI_List.xlsm";  
    my $Excel = Win32::OLE->GetActiveObject('Excel.Application')
        || Win32::OLE->new('Excel.Application', 'Quit');  # get alread
+y active Excel
                                                          # applicatio
+n or open new
     $Book = $Excel->Workbooks->Open($excelfile); # open Excel file
     

     $Sheet = $Book->Worksheets(3);       

     # select worksheet number 1
    $array = $Sheet->Range("B1:E40")->{'Value'};        # get the cont
+ents
    $Book->Close;
    $i=0;
    $j=0;
    foreach  $ref_array (@$array) {                     # loop through
+ the array
                                   $i++;  

                                   $j=0;
        foreach  $scalar (@$ref_array) {
                  $AOA[$i][$j]="$scalar";
                  $j++;
                  print $j;
        }
       
    } 
print "$AOA[1][1]";
[download]