use Win32::DriveInfo;

my $file = 'C:\test\file.txt';

sub fileSizeBlocks {
    my $file = shift;

    my ($drive) = $file =~ /^([A-Z])/;
    my ( $SectorsPerCluster, $BytesPerSector )
      = ( Win32::DriveInfo::DriveSpace($drive) )[ 0, 1 ];
    my $blockSizeBytes = $SectorsPerCluster * $BytesPerSector;

    my $fileSizeBytes = ( stat($file) )[7];
    
    my $blocks = int( $fileSizeBytes / $blockSizeBytes );
    $blocks++ if ( $fileSizeBytes % $blockSizeBytes );
        
    return $blockSizeBytes * $blocks;
}

say "Datei '$file' ist ", fileSizeBlocks($file), " groß";