Regular expression syntax
The Regex() function in Media Center's expression language supporting regular expression pattern matching is implemented using external regular expression libraries.
Media Center 26 and Later
Media Center 26 and later uses the standard regex implementation available in newer versions of C++, using the default ECMAScript grammar. It's the same syntax as the boost regex, just without a megabyte or two of additional dependencies. Note that this update may have occurred earlier than Media Center 26, but was first mentioned during its development cycle.
Media Center 19 and Later
In Media Center 19, the Regex() function is implemented using the Boost C++ library, version 1.54. While Boost supports several flavors of regular expressions, the mode enabled in Media Center is the Perl Regular Expression Syntax.