You don't need the flip flop or the other map if you use two separate Tr()'s: 
print $q->table( {-border=>"1"},
  map {
    $q->Tr([
      $q->td( {-rowspan=>'2'},$_ ) 
      . $q->td( $tab{$_}->[0] )
    ])
    . $q ->Tr([$q->td( $tab{$_}->[1] )])
  } sort keys %tab
);

[download]

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

In reply to (jeffa) Re: Getting CGI to emit table cells with rowspan attribute by jeffa
in thread Getting CGI to emit table cells with rowspan attribute by grinder

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