function letter(str)
  return unicode["utf8"].sub(str,1)
end

Ok, here is MWE. I keep getting
Forbidden control sequence found while scanning definition of \lst@temp emphstyle=[1]\color{red}}

\documentclass[11pt,notitlepage]{article}
\usepackage{listings}
\usepackage{color}
\begin{document}
\begin{tabular}{|p{6.7in}|}\hline
\ifdefined\HCode
\lstset{numbers=none}
\lstinputlisting{e100.m}
\else
\lstset{language=Matlab,
breaklines=true,
morekeywords={matlab2tikz},
keywordstyle=\color{blue},
morekeywords=[2]{1},
keywordstyle=[2]{\color{black}},
identifierstyle=\color{black},
stringstyle=\color{mylilas},
commentstyle=\color{mygreen},
showstringspaces=false,
numbers=left,
numberstyle={\tiny \color{black}},

\documentclass[11pt,notitlepage]{article}
\usepackage{listings}
\usepackage{color}

\definecolor{mygreen}{RGB}{28,172,0}
\definecolor{mylilas}{RGB}{170,55,241}


\begin{document}

\begin{tabular}{|p{6.7in}|}\hline

\ifdefined\HCode
\lstset{numbers=none}
\lstinputlisting{e100.m}
\else
\lstset{language=Matlab,
numbers=none,
breaklines=true,
morekeywords={matlab2tikz},
keywordstyle=\color{blue},
morekeywords=[2]{1},
keywordstyle=[2]{\color{black}},
identifierstyle=\color{black},
stringstyle=\color{mylilas},

\documentclass[11pt,notitlepage]{article}
\usepackage{listings}
\usepackage{color}

\definecolor{mygreen}{RGB}{28,172,0}
\definecolor{mylilas}{RGB}{170,55,241}


\begin{document}

\begin{tabular}{|p{6.7in}|}\hline
{
\ifdefined\HCode
\lstset{numbers=none}
\lstinputlisting{e100.m}
\else
\lstset{language=Matlab,
numbers=none,
breaklines=true,
morekeywords={matlab2tikz},
keywordstyle=\color{blue},
morekeywords=[2]{1},
keywordstyle=[2]{\color{black}},
identifierstyle=\color{black},
stringstyle=\color{mylilas},

tex4ht is nice. I can include raw HTML in Latex and show an animated gif file, all from one latex source file. If pdf is generated then use .png, else use animation

\ifdefined\HCode
\ScriptEnv{html}
   {\NoFonts\hfill\break}
   {\EndNoFonts}

  \begin{html}
  <p><IMG SRC="movie.gif" ALT="some text" WIDTH=350></p>
  \end{html}
\else
\includegraphics[scale=.7]{plot.png}
\fi

Psmith, the TeX bot, in fixed font mode:

#  (character)
number sign
ASCII | 35   (hex: 23  |  octal: 043  |  binary: 00100011)
Unicode | U+0023 (decimal: 35)
HTML | #
US English keyboard  |  United Kingdom keyboard  |  Chinese ChaJei keyboard  |  Japanese keyboard  |  German keyboard  |  Arabic (101) keyboard
punctuation
Unicode | basic Latin  (0 through 127)  (128 characters)
ISO 8859 | ISO 8859-1 (Latin-1)  (character 35)
\:2114 (l b bar symbol)  |  sharp (music sharp sign)