\noindent
{\setbox1=\hbox to 2000000sp{$\{abc\}$}%
\pdfxform 1
\setbox2=\vbox{\hbox to 12000000sp{$\{$2:$<$F1:\pdfrefxform\pdflastxform$>\}$}}%
\pdfxform 2
\setbox3=\vbox{\hbox to 20000000sp{\hbox to 2000000sp{ZTZ}$\{$3:$<$F2:\pdfrefxform2$>\}$}}%
\pdfxform 3
\hbox to 1000000sp{XX}%
$<$F3:\pdfrefxform3$>$\hbox to 2000000sp{XXX}%
%
}%
\end