For more details on PCRE2 usage in R 3.x, see: 7d25524f8b/m4/R.m4 (L3056-L3058) 7d25524f8b/m4/R.m4 (L3139-L3155)
7d25524f8b/m4/R.m4 (L3056-L3058)
7d25524f8b/m4/R.m4 (L3139-L3155)