We are using the following form:

<form action="https://onyen.unc.edu/cgi-bin/unc_id/authenticator.pl" method="POST">
  <input type="hidden" name="cookie"     value="123-bc-398z-45">
  <input type="hidden" name="orig"       value="<a href='http://tarna.oit.unc.edu/~utoddl/authtest.html'>orig</a>">

  <input type="hidden" name="title"      value="JoeBob's UNC-Only WebSite Login">

  <input type="hidden" name="target"     value="http://tarna.oit.unc.edu/cgi-bin/dumpvars.pl">

  <input type="hidden" name="textpass"       value="Select your division's color.">
  <input type="hidden" name="buttonlistpass" value="Green,Blue,Red">

  <input type="hidden" name="textfail"       value="<center>Oops! Pick one of these instead.</center>">
  <input type="hidden" name="buttonlistfail" value="Beg,Grovel,Whine">

  <input type="submit" name="submit"     value="Authenticate">
</form>

This one uses the TEST version of the authenticator.

<form action="https://onyen.unc.edu/cgi-bin/unc_id/authenticator.test.pl" method="POST">
  <input type="hidden" name="cookie"     value="123-bc-398z-45">
  <input type="hidden" name="orig"       value="<a href='http://tarna.oit.unc.edu/~utoddl/authtest.html'>orig</a>">

  <input type="hidden" name="title"      value="JoeBob's UNC-Only WebSite Login">

  <input type="hidden" name="target"     value="http://tarna.oit.unc.edu/cgi-bin/dumpvars.pl">
  <input type="hidden" name="targetfail" value="http://tarna.oit.unc.edu/cgi-bin/dumpvars.pl">

  <input type="hidden" name="textpass"       value="Select your division's color.">
  <input type="hidden" name="buttonlistpass" value="Green,Blue,Red">

  <input type="hidden" name="textfail"       value="Bzzzt! You FAILED! Choose you fate.">
  <input type="hidden" name="buttonlistfail" value="Beg,Grovel,Whine">

  <input type="submit" name="submit"     value="Authenticate">
</form>