If it's not going to appear twice on the same line:

my $seen=0;
while(<DATA>) {
  if ($seen) { s{<cnt>Germany</cnt>}{<TAB>} }
  else { $seen ||= m{<cnt>Germany</cnt>} }
  print;
}
__DATA__
<cnt>Germany</cnt><cmp>ALLIANZ INSURANCE</cmp>
<cnt>Germany</cnt><cmp>ALLIANZ PARKWAY</cmp>
<cnt>Germany</cnt><cmp>ALLIED DOMECQ</cmp>
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