Can you include a counter (this is how I've done it in the past..)?

  my $count = 0;
  while ( my $row = $sth->fetchrow_arrayref() )
  {
      $count++;
      # do something with $row..
  }
  print( "There were $count row(s)\n" );
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I know what you're asking and it's a worthy question, I just haven't tried working it out for myself because I've just used either of the two techniques I've mentioned instead.