Square bracket version of \left-brace markup

[Aaron Hill]

I am currently using \left-brace as a means for grouping multiple lyric 
lines:

%%%%
\version "2.19.80"

lyricBracket = \markup {
  \hspace #1 \translate #'(0 . 0.75) \left-brace #40
}

\relative c' { c4 d e2 | g8 f e4 c2 }
\addlyrics {
  \repeat unfold 3 \skip 1
  Mul -- ti -- ple lines
}
\addlyrics {
  Sin -- gle line
  \set stanza = \lyricBracket
  Mul -- ti -- ple lines
}
\addlyrics {
  \repeat unfold 3 \skip 1
  Mul -- ti -- ple lines
}
%%%%

This works fine, with a little manual adjustment of the brace size and 
spacing.  However, I would prefer to use a square bracket instead of the 
curly brace.  It seems like I will have to manually "draw" the bracket 
using markup functions and/or custom PostScript.

Has anyone here attempted something like this and can offer advice?

-- Aaron Hill