f1131623_sion_Reference__Special_Groups__Description
[Feature] Branch reset group [Syntax] (?|regex) [Example] (x)(?|(a)|(bc)|(def))\2 matches xaa, xbcbc, or xdefdef with the first group capturing x and the second group capturing a, bc, or def [JGsoft] no [.NET] no [Java] no [Perl] 5.10 [PCRE] 7.2 [PCRE2] YES [PHP] 5.2.4 [Delphi] YES [R] YES [JavaScript] no [VBScript] no [XRegExp] no [Python] no [Ruby] no [std::regex] no [Tcl ARE] no [POSIX BRE] no [POSIX ERE] no [GNU BRE] no [GNU ERE] no [Oracle] no [XML] no [XPath] no [Description] 
If the regex inside the branch reset group has multiple alternatives with capturing groups, then the capturing group numbers are the same in all the alternatives.
Regular Expression Reference: Special Groups