note ikegami Oops, I read the problem too fast. Fix: <c> $test =~ s{ ( <a\s (?:(?!target=|>).)* href="http:// (?:(?!target=|>).)* ) (?=>) }{$1 target="_blank"}xsgi; </c> <p>Alternatively, the following *might* be faster, especially considering <c>href</c> is usually the first attribute: <c> $test =~ s{ ( <a\s (?:(?!href=|target=|>).)* href="http:// (?:(?!target=|>).)* ) (?=>) }{$1 target="_blank"}xsgi; </c> <p>Tested. <p><b>Update</b>: Collapsed <c>(?!..re1..)(?!..re2..)</c> into <c>(?!..re1..|..re2..)</c> 544944 544953