...

   foreach my $worksheet (@{$excel_sheet -> {Worksheet}}) {
        
    $worksheet -> {MaxRow} ||= $worksheet -> {MinRow};

    # Skip worksheet if it doesn't contain data.
    next if $worksheet -> {MinRow} > $worksheet -> {MaxRow};
    
    foreach my $row ($worksheet->{MinRow} .. $worksheet->{MaxRow}) {

      # Send flag as DONE once it reach the end of file or if there is no data
      send_data( 
		   zipcode => 'DONE',  # Flag
                  );
		  
      # Correct values or skip them:
      next unless defined $worksheet->{Cells}[$row][0]->{Val};
      
      warn Dumper $worksheet->{Cells}[$row][0]->{Val};
      
      if ( $worksheet->{Cells}[$row][0]->{Val} =~ /^\d{5}/ ) {

        my $xlsx_rows = $worksheet->{Cells}[$row];
	
        # Send data
        send_data( 
                   zipcode    => $xlsx_rows->[0]->{Val}  || '',
		   firstname  => $xlsx_rows->[1]->{Val}  || '',
		   lastname   => $xlsx_rows->[2]->{Val}  || '',
                             
                           );
       
     }
      
    }

  }
  
...