And the problem is...? Given this is a perl site, I think the exhortation to generate text given your @userids is implicit.

  <tmpl_loop userids>
    <input type="checkbox" name="ids" value="<tmpl_var name>">
  </tmpl_loop>
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and in perl

  my %tmpl_vars = ( userids => map { {name => $_} } @userids );
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assuming you're using HTML::Template. Modify as appropriate for your own templating system. You are using a templating system, right?