Option -P now uses the JIT-optimized PCRE2 library when PCRE2 is installed, instead of Boost.Regex. Boost.Regex may still be used as an alternative library to PCRE2 with ./build.sh --enable-color --without-pcre2. The internal regex converters of ugrep automatically produce regex patterns that are suitable for PCRE2 or for Boost.Regex, to match Unicode (default) and raw binary with option -U. Updated Dockerfile to build ugrep with PCRE2 for ugrep option -P.