regex delimiters issue

There seems to be an unnecessary requirement to use ‘/’ as regular expression delimiters. This is quite unfortunate as ‘/’ is likely to occur in the expression and have to be escaped (as illustrated in the examples). This is not a requirement of PHP.

/\/something\// would be simpler and less error-prone as (for example) %/something/%

In validate_regex(), replace:

if ( ! preg_match( '/^\/.*\/$/', $regex ) ) {
     $regex = '/' . $regex . '/';
}

with

if ( substr($regex, 0, 1) !== substr($regex, -1) ) {
     $regex = '@' . $regex . '@';
}

(untested example).