function matchPattern(pattern, pos, text, lookbehind) {
		pattern.lastIndex = pos;
		var match = pattern.exec(text);
		if (match && lookbehind && match[1]) {
			// change the match to remove the text matched by the Prism lookbehind group
			var lookbehindLength = match[1].length;
			match.index += lookbehindLength;
			match[0] = match[0].slice(lookbehindLength);
		}
		return match;
	}
@callback HookCallback
@param {Object<string, any>} env The environment variables of the hook.
@returns {void}
@global
@public