-% my $class = '';
-% $class .= ' numeric' if $numeric->{$col};
-% $class .= ' changed' if $cols_changed->{$col};
-% $class =~ s/^ / class="/ && $class =~ s/$/"/;
-<td<%== $class %>>
+% my @class ;
+% push @class, 'numeric' if $numeric->{$col};
+% if ( defined $cols_changed->{$col} ) {
+% push @class, $cols_changed->{$col} ? 'changed' : 'used';
+% }
+<td class="<%= join(' ',@class) %>">