Reading up on the current spec, apparently a PCRE can do recursive calls. https://www.pcre.org/original/doc/html/pcrepattern.html#SEC23 https://www.pcre.org/or

Reading up on the current spec, apparently a PCRE can do recursive calls. https://www.pcre.org/original/doc/html/pcrepattern.html#SEC23 https://www.pcre.org/original/doc/html/pcrepattern.html#SEC2... \( ( [^()]++ | (?R) )* \) https://regex101.com/r/eBtSTM/1 https://regex101.com/r/eBtSTM/1 for a slightly different formulation of that regex.