Use `shortvrb` without needing to end the command manually

Question

Currently, using shortvrb, it's possible to define a single character to start, by itself, an inline verbatim command:

\documentclass{article}
\usepackage{shortvrb}

\begin{document}
\MakeShortVerb{\|}
foo |this is verbatim|
\end{document}

or similarly, with fancyvrb,

\documentclass{article}
\usepackage{fancyvrb}

\begin{document}
\DefineShortVerb{\|}
foo |this is verbatim|
\end{document}

In both cases -- as with \verb!some verbatim text! -- the symbol is required again to end the verbatim portion. If it's left out, an error similar to "\verb ended by end of line" is produced.

---

Is there a way to (re)define \MakeShortVerb or similar, such that the newline will merely end the command, rather than producing an error? Ideally, one could then write something like:

\DefineAsymmetricVerb{\|}
This is some regular text.
Now some verbatim code that only needs a symbol at the start of the line, like:
| if 1 == 1
|     print 'All is well'

This would allow blocks (or single lines) of verbatim text without the clutter of

| if 1 == 1                |
|     print 'All is well'  |

or

\begin{verbatim}
 if 1 == 1
     print 'All is well'
\end{verbatim}

Answer 1

You can, but you shouldn't.

\documentclass{article}

\makeatletter
\catcode`|=\active
\def|{%
  \par
  \begingroup
  \parindent\z@\mbox{}%
  \owj@eol\catcode`\^^M=\active
  \let\do\@makeother\dospecials
  \verbatim@font\@noligs
  \@vobeyspaces\frenchspacing
}
\def\owj@par{\par\endgroup}
\begingroup\lccode`~=`\^^M\lowercase{\endgroup
  \def\owj@eol{\let~\owj@par}
}
\makeatother

\begin{document}

This is some regular text.
Now some verbatim code that only needs a symbol at the start of the line, like:
| if 1 == 1
|     print 'All is well'
|
| else
|     error
| fi
\noindent This is some regular text

\end{document}