cant say i fully get where your going with this, but it looks a lot like a similar problem i had; turning a flat table into a nested loop, grouped by a particular field in the table?.
Heres the gist of what I did

    my @tabular  = $dbi->array_of_hashrefs_please();

    # move into a hash (keyed by category) of array of hashrefs (rows)
    my %categories;
    foreach( @tabular )
    {
        my $entry = $_->{ FIELD_I_WANT_TO_SORT_BY };
        if ( $categories{$entry} == undef )   
        { 
            $categories{$entry} = [$_] ;        
        }
        else                                  
        { 
            push @{$categories{$entry}}, $_;    
        }
    }

    # now create nested loop based on category...

    my @nested_loop;
    foreach(sort keys %categories)
    {
       push @nested_loop, { category => $_, entries => $categories{$_}
+};
    }

    # add our nested loop to the template
    $template->param( my_loop => \@nested_loop);
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...with a tmpl something like...

    <tmpl_loop name="my_loop">
            <tmpl_var name="category">
            <tmpl_loop name="entries">
                <!-- inner loop data here -->
            </tmpl_loop>
    </tmpl_loop>
[download]

hope its of some use