$re = '/^#WAV\b.*(?:\R#WAV\b.*)*/m';
$str = '#WAV 001.wav
#WAV "something"
#WAV 21021029910291029.ogg
.....
#WAV 001.wav
#WAV "something"
#WAV 21021029910291029.ogg';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php