my $input=<<HERE;
<span>
              <span>
                <span style="color:#000000;">
                  <ix:nonNumeric name="uk-bus:PrincipalLocation-CityOr
+Town">London</ix:nonNumeric>
                </span>
              </span>
            </span>
HERE

$input=~s/<\/?span[^>]*>//g;

print $input;
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