SHELL_SCRIPT
  COMMANDS_LIST
    SIMPLE_COMMAND
      GENERIC_COMMAND_DIRECTIVE
        LITERAL
          PsiElement(word)('echo')
      PsiWhiteSpace(' ')
      SIMPLE_COMMAND_ELEMENT
        COMMAND_SUBSTITUTION_COMMAND
          PsiElement(OPEN_BACKQUOTE)('`')
          COMPOUND_LIST
            GENERIC_COMMAND_DIRECTIVE
              LITERAL
                PsiElement(word)('cat')
          PsiWhiteSpace(' ')
          PsiElement(CLOSE_BACKQUOTE)('`')
      LITERAL
        PsiElement(word)('cat')
      PsiWhiteSpace(' ')
      VARIABLE
        PsiElement(var)('$0')
      SIMPLE_COMMAND_ELEMENT
        COMMAND_SUBSTITUTION_COMMAND
          PsiElement(OPEN_BACKQUOTE)('`')
          PsiElement(CLOSE_BACKQUOTE)('`')