**LATEX 239**

The byte count does not include the `\documentclass` command nor any `\usepackage` commands. I would argue both count as using external packages, as the former includes definitions in an external .cls file, and usepackage is practically synonymous with an include statement. Output is a pdf file containing the 100 lines with no other text, formatted appropriately. [Try it at writelatex.com!](https://www.writelatex.com/1681410mgfzmq#/4192732/)

    \begin{document}\newcounter{a}\def\c{re a time }\def\d{een-hundreds we\c}\StrLen{\d}[\b]\forloop{a}{\parindent}{\value{a}<\b}{The eight\d for rum.\\The ninet\d for fun.\\The two-thousands a\c to run\\a civilized classroom.\\}\end{document}

Ungolfed:

    \documentclass{letter}

    \usepackage{forloop}
    \usepackage{parskip}
    \usepackage{xstring}
    \usepackage{nopageno}

    \begin{document}
    
    \newcounter{a}
    
    \def\c{re a time }
    \def\d{een-hundreds we\c}

    % Sets \b to be the length of \d, in characters, when fully expanded
    \StrLen{\d}[\b]

    % Loops over a from \parindent to \b
    % Note that parskip package sets \parindent to 0
    % and \b is 25 from the length of \d fully expanded
    \forloop{a}{\parindent}{\value{a}<\b}{
        The eight\d for rum.\\
        The ninet\d for fun.\\
        The two-thousands a\c to run\\
        a civilized classroom.\\
    }

    \end{document}