$re = '/\s*\bif\b.*?\b(then)\b|\s*\bfor\b.*?\b(to)\b|\s*\bto\b.*?\b(step)\b|\s*\belse\b.*?\b(if)\b|\s*\bsubroutine\b.*?\b(local)\b/';
$str = 'if then
for to
to step
else if
subroutine local';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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