load("sregex")$
regex_match("\\W[A-Z]", "Hello World!"); /* returns matched substring */
regex_match("\\W[A-Z]", "Hello world!"); /* returns false if no match */
regex_subst_first("4", "[Aa]", "Abracadabra!"); /* replaces first match */
regex_subst("4", "[Aa]", "Abracadabra!"); /* replaces all matches */