是否存在与案例环境相当的证明？

Question

cases 环境非常适合显示具有多个案例和简短描述的方程式，但对于显示具有多段案例的证明来说却很尴尬。是否有一组更像 HTML <dl>、<dt> 和 <dd> 标签的等效标签？类似于

\begin{proofcases}
\case Description of first case
\item Proof of first case.
\case Description of second case
\item Proof of second case.
\end{proofcases}

我想要输出类似

Then 

Foo is a bar. This description is long, cumberome and unieldy if it
has to be displayed using cases.  
     Baz is a blivit. This follows by the covering homotopy theorem. We
     don't need no stinking fiber bundles, and this proof is already too
     long. 
Foo is a widget 
     Baz is a descending chain. This follows because Cuius rei
     demonstrationem mirabilem sane detexi hanc marginis exiguitas non
     caperet. Apologies to Fermat. 

由

Then
<dl>
<dt>Foo is a bar.
This description is long, cumberome and unieldy if it has to be displayed
using cases. 
<dd>Baz is a blivit.
This follows by the covering homotopy theorem. 

We don't need no stinking fiber bundles, and this proof is already too long.
<dt>Foo is a widget
<dd>Baz is a descending chain.
This follows because Cuius rei demonstrationem mirabilem sane detexi hanc
marginis exiguitas non caperet. Apologies to Fermat.
</dl>

描述环境不适合，因为标签未换行。以下示例向右运行：

\begin{description}
\item%
  [
    This is an example of a very long label for an item of the
    description environment, running over multiple lines, in order
    to demonstrate why it is awkward to use that environment for
    cases of a proof.
  ]
  This is sample text for the description of a case with a long
  label, again running over multiple lines.
\item[short label] short description
\end{description}