This is boxen, a Common Lisp package that allows a programmer to write
Unicode box characters when delimiting strings, comments, and
sub-programs.  This preserves the indentation of text in the source
code, yet allows the text to sit naturally and obviously at the same
indent level as the source code surrounding it.  The best way to see
how it works is with an example.  All of the following expressions are
equivalent:

(setf *foo* "a
  hoo-ha
         of
            foos
")

(setf *foo* (format nil "~&a~
                         ~%  hoo-ha~
                         ~%         of~
                         ~%            foos~%"))

(setf *foo* ┌─────
            │a
            │  hoo-ha
            │         of
            │            foos
            └─────)

As many or as few #\BOX_DRAWINGS_LIGHT_HORIZONTAL characters may
occur after the opening #\BOX_DRAWINGS_LIGHT_DOWN_AND_RIGHT
character, forming a horizontal rule of any desired length,
although they may not be followed by anything but white space and a
single newline.  Each line thereafter must begin with optional
whitespace and a single #\BOX_DRAWINGS_LIGHT_VERTICAL (*not* a
#\VERTICAL_LINE).  Likewise, the final
#\BOX_DRAWINGS_LIGHT_UP_AND_RIGHT character may be followed by any
number of horizontals.  Blank lines within are not allowed.  The
#\BOX_DRAWINGS_LIGHT_VERTICAL always marks the left edge of the
line regardless of whitespace that occurs before it.  Emacs
functions to automatically align verticals are available. 

To a certain extent FORMAT ameliorates related problems in that
#\TILDE followed by #\NEWLINE or @ collapses subsequent whitespace,
but this is not useful when you want to preserve indentation.  The
boxy syntax is meant to suggest what you see in an editor window or
terminal more-or-less precisely.  Note that boxy syntax nests, even
when internal strings are poorly formed.  

Long "doc strings" are especially pretty in BOXEN -- I recommend
filling them with some sane descendant of markdown.  The author's main
intended use, however, is in writing programs that generate
configuration files for other software.  Often times these
configuration files are in a horribly broken language in which white
space, double quotes, and so forth, are significant, and embedding
them in yet another layer of slightly different string syntax is error
prone and ugly.  Embedding them in this layer of *extremely* different
string syntax seems preferable.

In addition to the string syntax, a comment syntax is provided, which
uses double lines.  Future work for this package involves tagging
double lined syntax on the top line, and perhaps invoking sub-parsers
to deal with their contents.  The result of evaluating a tagged double
lined string is a closure that (presumably) coughs up a string when
evaluated.

This package can be installed and built with asdf.  Link the boxen.asd
file into your systems directory (probabaly ~/.sbcl/systems) and do
the following at your CL-USER prompt:

    (asdf:operate 'asdf:load-op 'boxen)