f1131623_sion_Reference__Special_Groups__Description
[Feature] Negative lookahead [Syntax] (?!regex) [Example] t(?!s) matches the first t in streets. [JGsoft] YES [.NET] YES [Java] YES [Perl] YES [PCRE] YES [PCRE2] YES [PHP] YES [Delphi] YES [R] YES [JavaScript] YES [VBScript] YES [XRegExp] YES [Python] YES [Ruby] YES [std::regex] ECMA [Tcl ARE] YES [POSIX BRE] no [POSIX ERE] no [GNU BRE] no [GNU ERE] no [Oracle] no [XML] no [XPath] no [Description] 
Similar to positive lookahead, except that negative lookahead only succeeds if the regex inside the lookahead fails to match.
Regular Expression Reference: Special Groups