One question - what are you going to use the string for?

If it's going to used in XML / HTML, you should also check there are no ASCII control codes other than \r \n and \t e.g.

if ( $str =~ /[^\x09\x0A\x0D\x20-\x7E]/g ){
    print "Contains invalid characters";
}
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See HOWTO Avoid Being Called a Bozo When Producing XML.