PREFIX ex: <http://a.example>
PREFIX sx: <http://www.w3.org/ns/shex#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

[] a sx:Schema ;
    sx:shapes (<http://a.example/S1>);
    <http://www.w3.org/ns/shex#startActs> ([
      a <http://www.w3.org/ns/shex#SemAct>;
      <http://www.w3.org/ns/shex#code> " print(\"startAct 1\") ";
      <http://www.w3.org/ns/shex#name> <http://shex.io/extensions/Test/>
    ] [
      a <http://www.w3.org/ns/shex#SemAct>;
      <http://www.w3.org/ns/shex#code> " fail(\"startAct 2\") ";
      <http://www.w3.org/ns/shex#name> <http://shex.io/extensions/Test/>
    ] [
      a <http://www.w3.org/ns/shex#SemAct>;
      <http://www.w3.org/ns/shex#code> " print(\"startAct 3\") ";
      <http://www.w3.org/ns/shex#name> <http://shex.io/extensions/Test/>
    ]) .

<http://a.example/S1> a sx:ShapeDecl ; sx:shapeExpr [ a sx:Shape ;
    sx:expression [ a sx:TripleConstraint ;
            sx:predicate <http://a.example/p1> ] ] .