1# BRE Quantifiers 2ab\?c b abc abc 3ab\+c b abc abc 4# BRE Branching 5abc\|de b abc abc 6a\|b\|c b abc a 7\(ab\|bc\) b abcd ab 8# ERE Backrefs 9(ab)\1 - ab 10(ab)\1 - abab abab 11\1(ab) C ESUBREG 12(a)(b)(c)(d)(e)(f)(g)(h)(i)\9 - abcdefghii abcdefghii 13# \w, \W, \s, \S (alnum, ^alnum, space, ^space) 14\w+ - -%@a0X- a0X 15\w\+ b -%@a0X- a0X 16\s+ - aSNTb SNT 17\s\+ b aSNTb SNT 18# Word boundaries (\b, \B, \<, \>, \`, \') 19# (is/not boundary, start/end word, start/end subject string) 20\babc\b & <abc> abc 21\<abc\> & <abc> abc 22\Babc\B & abc 23\B[abc]\B & <abc> b 24\B[abc]+ - <abc> bc 25\B[abc]\+ b <abc> bc 26\`abc & abc abc 27abc\' & abc abc 28\`abc\' & abc abc 29\`.+\' - abNc abNc 30\`.\+\' b abNc abNc 31(\`a) - Na 32(a\`) - aN 33(a\') - aN 34(\'a) - Na 35