Given tex (Define complex environment):
  \begin{complexenvironment}[option1,
    option2]{first extra argument}
    {second extra
    argument}
    Hello world!
  \end{complexenvironment}

Do (Delete environment (excluding)):
  die

Expect tex (Verify):
  \begin{complexenvironment}[option1,
    option2]{first extra argument}
    {second extra
    argument}
  \end{complexenvironment}

Do (Delete environment (including)):
  dae

Expect tex (Verify):