### venn

    // Usage: pl -gif venn.htm
    //
    // Venn diagram example

    #proc page
    pagesize: 8 7
    title: Venn diagram example

    #proc venndisk
      location: 3 4
      area: 8
      color: green
      label: set A

    #proc venndisk
      location: 5 4
      area: 7
      color: lavender
      label: set B

    #proc venndisk
      location: 4 2.6
      area: 4
      color: orange
      label: set C

    #proc legend
      location: 2 1.3
      format: across