title: How may I convert a three-digit Arabic number (Perl [0-9][0-9][0-9]) to a three-digit English representation ([zero-nine][zero-nine][zero-nine])
body: <p>The alternative is to use Roman numerals, for which a package is
  available.  I am using the LaTeX catchfile package and the \input{}
  command to associate a title in a set of TITLE files with \section{}
  commands in a set of DOCUMENT files.</p>
  <p>I would like to have a file of catchfile definitions, with records
  such as:</p>
  <pre><code>\CatchFileDef{\t-001}{title-001.tex}{}
  
  \CatchFileDef{\t-002}{title-002.tex}{}
  
  \CatchFileDef{\t-003}{title-003.tex}{}
  
  But LaTeX does not allow numerical labels such as &quot;\title-003&quot;.
  
  Roman numerals are workable:
  
  \CatchFileDef{\ti}{title-001.tex}{}
  
  \CatchFileDef{\tii}{title-002.tex}{}
  
  \CatchFileDef{\tiii}{title-003.tex}{}
  
  but are ugly in comparison with:
  
  \CatchFileDef{\tzerozeroone}{title-001.tex}{}
  
  \CatchFileDef{\tzerozerotwo}{title-002.tex}{}
  
  \CatchFileDef{\tzerozerothree}{title-003.tex}{}
  </code></pre>