global

def bibtagsys(bib, anchor=nil, stand_alone=true)
  if bib =~ /\Arfc(\d+)/i
    rfc4d = "%04d" % $1.to_i
    [bib.upcase,
     "#{XML_RESOURCE_ORG_PREFIX}/bibxml/reference.RFC.#{rfc4d}.xml"]
  elsif $options.v3 && bib =~ /\A(bcp|std)(\d+)/i
    n4d = "%04d" % $2.to_i
    [bib.upcase,
     "#{XML_RESOURCE_ORG_PREFIX}/bibxml-rfcsubseries-new/reference.#{$1.upcase}.#{n4d}.xml"]
  elsif bib =~ /\A([-A-Z0-9]+)\./ &&
        (xro = Kramdown::Converter::Rfc2629::XML_RESOURCE_ORG_MAP[$1])
    dir, _ttl, rewrite_anchor = xro
    bib1 = ::Kramdown::Parser::RFC2629Kramdown.idref_cleanup(bib)
    if anchor && bib1 != anchor
      if rewrite_anchor
        a = %{?anchor=#{anchor}}
      else
        if !stand_alone
          warn "*** selecting a custom anchor '#{anchor}' for '#{bib1}' requires stand_alone mode"
          warn "    the output will need manual editing to correct this"
        end
      end
    end
    [bib1,
     "#{XML_RESOURCE_ORG_PREFIX}/#{dir}/reference.#{bib}.xml#{a}"]
  end
end