reuse.xml

<svg>
  <!-- Draw a 'pipeline' shape using a path element -->
  <style>
    .coin { fill: gold; stroke: silver; }
  </style>

  <specs>
    <path id="pipeline" d="M $pipe_x {{$pipe_y + $pipe_w / 4}}
      a {{$pipe_w / 2}} {{$pipe_w / 4}} 0 0 0 $pipe_w 0
      a {{$pipe_w / 2}} {{$pipe_w / 4}} 0 0 0 {{-$pipe_w}} 0
      v {{$pipe_h - $pipe_w / 2}}
      a {{$pipe_w / 2}} {{$pipe_w / 4}} 0 0 0 $pipe_w 0
      v {{-$pipe_h + $pipe_w / 2}}" />

    <path id="box3d" d="M $target@tl l 2 -2 h $target~w l -2 2 z M $target@tr v $target~h l 2 -2 v -$target~h z"/>
  </specs>

  <reuse href="#pipeline" pipe_w="10" pipe_h="40" pipe_x="10" pipe_y="10" style="fill:red"/>

  <reuse id="p1" href="#pipeline" pipe_w="20" pipe_h="13" pipe_x="30" pipe_y="10" class="coin"/>

  <reuse id="p2" href="#pipeline" pipe_w="20" pipe_h="20" pipe_x="30" pipe_y="25" style="stroke-width: 0.1; fill: limegreen;"/>

  <rect id="border" surround="#p1 #p2" margin="4"/>
  <reuse href="#box3d" target="#border" style="fill:lightgrey"/>

  <rect id="box" xy="10 60" wh="40 10"/>
  <reuse href="#box3d" target="#box" style="fill:lightgrey"/>
</svg>