/the quick brown fox/ the quick brown fox The quick brown FOX What do you know about the quick brown fox? What do you know about THE QUICK BROWN FOX? /The quick brown fox/i the quick brown fox The quick brown FOX What do you know about the quick brown fox? What do you know about THE QUICK BROWN FOX? /abcd\t\n\r\f\a\e\071\x3b\$\\\?caxyz/ abcd\t\n\r\f\a\e9;\$\\?caxyz /a*abc?xyz+pqr{3}ab{2,}xy{4,5}pq{0,6}AB{0,}zz/ abxyzpqrrrabbxyyyypqAzz abxyzpqrrrabbxyyyypqAzz aabxyzpqrrrabbxyyyypqAzz aaabxyzpqrrrabbxyyyypqAzz aaaabxyzpqrrrabbxyyyypqAzz abcxyzpqrrrabbxyyyypqAzz aabcxyzpqrrrabbxyyyypqAzz aaabcxyzpqrrrabbxyyyypAzz aaabcxyzpqrrrabbxyyyypqAzz aaabcxyzpqrrrabbxyyyypqqAzz aaabcxyzpqrrrabbxyyyypqqqAzz aaabcxyzpqrrrabbxyyyypqqqqAzz aaabcxyzpqrrrabbxyyyypqqqqqAzz aaabcxyzpqrrrabbxyyyypqqqqqqAzz aaaabcxyzpqrrrabbxyyyypqAzz abxyzzpqrrrabbxyyyypqAzz aabxyzzzpqrrrabbxyyyypqAzz aaabxyzzzzpqrrrabbxyyyypqAzz aaaabxyzzzzpqrrrabbxyyyypqAzz abcxyzzpqrrrabbxyyyypqAzz aabcxyzzzpqrrrabbxyyyypqAzz aaabcxyzzzzpqrrrabbxyyyypqAzz aaaabcxyzzzzpqrrrabbxyyyypqAzz aaaabcxyzzzzpqrrrabbbxyyyypqAzz aaaabcxyzzzzpqrrrabbbxyyyyypqAzz aaabcxyzpqrrrabbxyyyypABzz aaabcxyzpqrrrabbxyyyypABBzz >>>aaabxyzpqrrrabbxyyyypqAzz >aaaabxyzpqrrrabbxyyyypqAzz >>>>abcxyzpqrrrabbxyyyypqAzz *** Failers abxyzpqrrabbxyyyypqAzz abxyzpqrrrrabbxyyyypqAzz abxyzpqrrrabxyyyypqAzz aaaabcxyzzzzpqrrrabbbxyyyyyypqAzz aaaabcxyzzzzpqrrrabbbxyyypqAzz aaabcxyzpqrrrabbxyyyypqqqqqqqAzz /^(abc){1,2}zz/ abczz abcabczz *** Failers zz abcabcabczz >>abczz /^(b+?|a){1,2}?c/ bc bbc bbbc bac bbac aac abbbbbbbbbbbc bbbbbbbbbbbac *** Failers aaac abbbbbbbbbbbac /^(b+|a){1,2}c/ bc bbc bbbc bac bbac aac abbbbbbbbbbbc bbbbbbbbbbbac *** Failers aaac abbbbbbbbbbbac /^(b+|a){1,2}?bc/ bbc /^(b*|ba){1,2}?bc/ babc bbabc bababc *** Failers bababbc babababc /^(ba|b*){1,2}?bc/ babc bbabc bababc *** Failers bababbc babababc /^\ca\cA\c[\c{\c:/ \x01\x01\e;z /^[ab\]cde]/ athing bthing ]thing cthing dthing ething *** Failers fthing [thing \\thing /^[]cde]/ ]thing cthing dthing ething *** Failers athing fthing /^[^ab\]cde]/ fthing [thing \\thing *** Failers athing bthing ]thing cthing dthing ething /^[^]cde]/ athing fthing *** Failers ]thing cthing dthing ething /^\/ /^/ /^[0-9]+$/ 0 1 2 3 4 5 6 7 8 9 10 100 *** Failers abc /^.*nter/ enter inter uponter /^xxx[0-9]+$/ xxx0 xxx1234 *** Failers xxx /^.+[0-9][0-9][0-9]$/ x123 xx123 123456 *** Failers 123 x1234 /^.+?[0-9][0-9][0-9]$/ x123 xx123 123456 *** Failers 123 x1234 /^([^!]+)!(.+)=apquxz\.ixr\.zzz\.ac\.uk$/ abc!pqr=apquxz.ixr.zzz.ac.uk *** Failers !pqr=apquxz.ixr.zzz.ac.uk abc!=apquxz.ixr.zzz.ac.uk abc!pqr=apquxz:ixr.zzz.ac.uk abc!pqr=apquxz.ixr.zzz.ac.ukk /:/ Well, we need a colon: somewhere *** Fail if we don't /([\da-f:]+)$/i 0abc abc fed E :: 5f03:12C0::932e fed def Any old stuff *** Failers 0zzz gzzz fed\x20 Any old rubbish /^.*\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/ .1.2.3 A.12.123.0 *** Failers .1.2.3333 1.2.3 1234.2.3 /^(\d+)\s+IN\s+SOA\s+(\S+)\s+(\S+)\s*\(\s*$/ 1 IN SOA non-sp1 non-sp2( 1 IN SOA non-sp1 non-sp2 ( *** Failers 1IN SOA non-sp1 non-sp2( /^[a-zA-Z\d][a-zA-Z\d\-]*(\.[a-zA-Z\d][a-zA-z\d\-]*)*\.$/ a. Z. 2. ab-c.pq-r. sxk.zzz.ac.uk. x-.y-. *** Failers -abc.peq. /^\*\.[a-z]([a-z\-\d]*[a-z\d]+)?(\.[a-z]([a-z\-\d]*[a-z\d]+)?)*$/ *.a *.b0-a *.c3-b.c *.c-a.b-c *** Failers *.0 *.a- *.a-b.c- *.c-a.0-c /^(?=ab(de))(abd)(e)/ abde /^(?!(ab)de|x)(abd)(f)/ abdf /^(?=(ab(cd)))(ab)/ abcd /^[\da-f](\.[\da-f])*$/i a.b.c.d A.B.C.D a.b.c.1.2.3.C /^\".*\"\s*(;.*)?$/ \"1234\" \"abcd\" ; \"\" ; rhubarb *** Failers \"1234\" : things /^$/ \ *** Failers / ^ a (?# begins with a) b\sc (?# then b c) $ (?# then end)/x ab c *** Failers abc ab cde /(?x) ^ a (?# begins with a) b\sc (?# then b c) $ (?# then end)/ ab c *** Failers abc ab cde /^ a\ b[c ]d $/x a bcd a b d *** Failers abcd ab d /^(a(b(c)))(d(e(f)))(h(i(j)))(k(l(m)))$/ abcdefhijklm /^(?:a(b(c)))(?:d(e(f)))(?:h(i(j)))(?:k(l(m)))$/ abcdefhijklm /^[\w][\W][\s][\S][\d][\D][\b][\n][\c]][\022]/ a+ Z0+\x08\n\x1d\x12 /^[.^$|()*+?{,}]+/ .^\$(*+)|{?,?} /^a*\w/ z az aaaz a aa aaaa a+ aa+ /^a*?\w/ z az aaaz a aa aaaa a+ aa+ /^a+\w/ az aaaz aa aaaa aa+ /^a+?\w/ az aaaz aa aaaa aa+ /^\d{8}\w{2,}/ 1234567890 12345678ab 12345678__ *** Failers 1234567 /^[aeiou\d]{4,5}$/ uoie 1234 12345 aaaaa *** Failers 123456 /^[aeiou\d]{4,5}?/ uoie 1234 12345 aaaaa 123456 /\A(abc|def)=(\1){2,3}\Z/ abc=abcabc def=defdefdef *** Failers abc=defdef /^(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\11*(\3\4)\1(?#)2$/ abcdefghijkcda2 abcdefghijkkkkcda2 /(cat(a(ract|tonic)|erpillar)) \1()2(3)/ cataract cataract23 catatonic catatonic23 caterpillar caterpillar23 /^From +([^ ]+) +[a-zA-Z][a-zA-Z][a-zA-Z] +[a-zA-Z][a-zA-Z][a-zA-Z] +[0-9]?[0-9] +[0-9][0-9]:[0-9][0-9]/ From abcd Mon Sep 01 12:33:02 1997 /^From\s+\S+\s+([a-zA-Z]{3}\s+){2}\d{1,2}\s+\d\d:\d\d/ From abcd Mon Sep 01 12:33:02 1997 From abcd Mon Sep 1 12:33:02 1997 *** Failers From abcd Sep 01 12:33:02 1997 /^12.34/s 12\n34 12\r34 /\w+(?=\t)/ the quick brown\t fox /foo(?!bar)(.*)/ foobar is foolish see? /(?:(?!foo)...|^.{0,2})bar(.*)/ foobar crowbar etc barrel 2barrel A barrel /^(\D*)(?=\d)(?!123)/ abc456 *** Failers abc123 /^1234 #comment in extended re /x 1234 /^abcd#rhubarb/x abcd /^(a)\1{2,3}(.)/ aaab aaaab aaaaab aaaaaab /(?!^)abc/ the abc *** Failers abc /(?=^)abc/ abc *** Failers the abc /^[ab]{1,3}(ab*|b)/ aabbbbb /^[ab]{1,3}?(ab*|b)/ aabbbbb /^[ab]{1,3}?(ab*?|b)/ aabbbbb /^[ab]{1,3}(ab*?|b)/ aabbbbb /abc\0def\00pqr\000xyz\0000AB/ abc\0def\00pqr\000xyz\0000AB abc456 abc\0def\00pqr\000xyz\0000ABCDE /abc\x0def\x00pqr\x000xyz\x0000AB/ abc\x0def\x00pqr\x000xyz\x0000AB abc456 abc\x0def\x00pqr\x000xyz\x0000ABCDE /^[\000-\037]/ \0A \01B \037C /\0*/ \0\0\0\0 /A\x0{2,3}Z/ The A\x0\x0Z An A\0\x0\0Z *** Failers A\0Z A\0\x0\0\x0Z /^(cow|)\1(bell)/ cowcowbell bell *** Failers cowbell /^\s/ \040abc \x0cabc \nabc \rabc \tabc *** Failers abc /^a b c/x abc /^(a|)\1*b/ ab aaaab b *** Failers acb /^(a|)\1+b/ aab aaaab b *** Failers ab /^(a|)\1?b/ ab aab b *** Failers acb /^(a|)\1{2}b/ aaab b *** Failers ab aab aaaab /^(a|)\1{2,3}b/ aaab aaaab b *** Failers ab aab aaaaab /ab{1,3}bc/ abbbbc abbbc abbc *** Failers abc abbbbbc /([^.]*)\.([^:]*):[T ]+(.*)/ track1.title:TBlah blah blah /([^.]*)\.([^:]*):[T ]+(.*)/i track1.title:TBlah blah blah /([^.]*)\.([^:]*):[t ]+(.*)/i track1.title:TBlah blah blah /^[W-c]+$/ WXY_^abc *** Failers wxy /^[W-c]+$/i WXY_^abc wxy_^ABC /^[\x3f-\x5F]+$/i WXY_^abc wxy_^ABC /^abc$/m abc qqq\nabc abc\nzzz qqq\nabc\nzzz /^abc$/ abc *** Failers qqq\nabc abc\nzzz qqq\nabc\nzzz /\Aabc\Z/m abc abc\n *** Failers qqq\nabc abc\nzzz qqq\nabc\nzzz /\A(.)*\Z/s abc\ndef /\A(.)*\Z/m *** Failers abc\ndef /(?:b)|(?::+)/ b::c c::b /[-az]+/ az- *** Failers b /[az-]+/ za- *** Failers b /[a\-z]+/ a-z *** Failers b /[a-z]+/ abcdxyz /[\d-]+/ 12-34 *** Failers aaa /[\d-z]+/ 12-34z *** Failers aaa /\x5c/ \\ /\x20Z/ the Zoo *** Failers Zulu /(abc)\1/i abcabc ABCabc abcABC /ab{3cd/ ab{3cd /ab{3,cd/ ab{3,cd /ab{3,4a}cd/ ab{3,4a}cd /{4,5a}bc/ {4,5a}bc /^a.b/ a\rb *** Failers a\nb /abc$/ abc abc\n *** Failers abc\ndef /(abc)\123/ abc\x53 /(abc)\223/ abc\x93 /(abc)\323/ abc\xd3 /abc\81/ abc\081 abc\0\x38\x31 /abc\91/ abc\091 abc\0\x39\x31 /(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(l)\12\123/ abcdefghijkllS /(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)\12\123/ abcdefghijk\12S /a{0}bc/ bc /(a|(bc)){0,0}?xyz/ xyz /abc[\10]de/ abc\010de /abc[\1]de/ abc\1de /(abc)[\1]de/ abc\1de /(?s)a.b/ a\nb /^([^a])([^\b])([^c]*)([^d]{3,4})/ baNOTccccd baNOTcccd baNOTccd bacccd *** Failers anything b\bc baccd /[^a]/ Abc /[^a]/i Abc /[^a]+/ AAAaAbc /[^a]+/i AAAaAbc /[^a]+/ bbb\nccc /[^k]$/ abc *** Failers abk /[^k]{2,3}$/ abc kbc kabc *** Failers abk akb akk /^\d{8,}\@.+[^k]$/ 12345678\@a.b.c.d 123456789\@x.y.z *** Failers 12345678\@x.y.uk 1234567\@a.b.c.d /(a)\1{8,}/ aaaaaaaaa aaaaaaaaaa *** Failers aaaaaaa /[^a]/ aaaabcd aaAabcd /[^a]/i aaaabcd aaAabcd /[^az]/ aaaabcd aaAabcd /[^az]/i aaaabcd aaAabcd /P[^*]TAIRE[^*]{1,6}?LL/ xxxxxxxxxxxPSTAIREISLLxxxxxxxxx /P[^*]TAIRE[^*]{1,}?LL/ xxxxxxxxxxxPSTAIREISLLxxxxxxxxx /(\.\d\d[1-9]?)\d+/ 1.230003938 1.875000282 1.235 /(\.\d\d((?=0)|\d(?=\d)))/ 1.230003938 1.875000282 *** Failers 1.235 /a(?)b/ ab /\b(foo)\s+(\w+)/i Food is on the foo table /foo(.*)bar/ The food is under the bar in the barn. /foo(.*?)bar/ The food is under the bar in the barn. /(.*)(\d*)/ I have 2 numbers: 53147 /(.*)(\d+)/ I have 2 numbers: 53147 /(.*?)(\d*)/ I have 2 numbers: 53147 /(.*?)(\d+)/ I have 2 numbers: 53147 /(.*)(\d+)$/ I have 2 numbers: 53147 /(.*?)(\d+)$/ I have 2 numbers: 53147 /(.*)\b(\d+)$/ I have 2 numbers: 53147 /(.*\D)(\d+)$/ I have 2 numbers: 53147 /^\D*(?!123)/ ABC123 /^(\D*)(?=\d)(?!123)/ ABC445 *** Failers ABC123 /^[W-]46]/ W46]789 -46]789 *** Failers Wall Zebra 42 [abcd] ]abcd[ /^[W-\]46]/ W46]789 Wall Zebra Xylophone 42 [abcd] ]abcd[ \\backslash *** Failers -46]789 well /\d\d\/\d\d\/\d\d\d\d/ 01/01/2000 /word (?:[a-zA-Z0-9]+ ){0,10}otherword/ word cat dog elephant mussel cow horse canary baboon snake shark otherword word cat dog elephant mussel cow horse canary baboon snake shark /word (?:[a-zA-Z0-9]+ ){0,300}otherword/ word cat dog elephant mussel cow horse canary baboon snake shark the quick brown fox and the lazy dog and several other words getting close to thirty by now I hope /^(a){0,0}/ bcd abc aab /^(a){0,1}/ bcd abc aab /^(a){0,2}/ bcd abc aab /^(a){0,3}/ bcd abc aab aaa /^(a){0,}/ bcd abc aab aaa aaaaaaaa /^(a){1,1}/ bcd abc aab /^(a){1,2}/ bcd abc aab /^(a){1,3}/ bcd abc aab aaa /^(a){1,}/ bcd abc aab aaa aaaaaaaa /.*\.gif/ borfle\nbib.gif\nno /.{0,}\.gif/ borfle\nbib.gif\nno /.*\.gif/m borfle\nbib.gif\nno /.*\.gif/s borfle\nbib.gif\nno /.*\.gif/ms borfle\nbib.gif\nno /.*$/ borfle\nbib.gif\nno /.*$/m borfle\nbib.gif\nno /.*$/s borfle\nbib.gif\nno /.*$/ms borfle\nbib.gif\nno /.*$/ borfle\nbib.gif\nno\n /.*$/m borfle\nbib.gif\nno\n /.*$/s borfle\nbib.gif\nno\n /.*$/ms borfle\nbib.gif\nno\n /(.*X|^B)/ abcde\n1234Xyz BarFoo *** Failers abcde\nBar /(.*X|^B)/m abcde\n1234Xyz BarFoo abcde\nBar /(.*X|^B)/s abcde\n1234Xyz BarFoo *** Failers abcde\nBar /(.*X|^B)/ms abcde\n1234Xyz BarFoo abcde\nBar /(?s)(.*X|^B)/ abcde\n1234Xyz BarFoo *** Failers abcde\nBar /(?s:.*X|^B)/ abcde\n1234Xyz BarFoo *** Failers abcde\nBar /^.*B/ **** Failers abc\nB /(?s)^.*B/ abc\nB /(?m)^.*B/ abc\nB /(?ms)^.*B/ abc\nB /(?ms)^B/ abc\nB /(?s)B$/ B\n /^[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]/ 123456654321 /^\d\d\d\d\d\d\d\d\d\d\d\d/ 123456654321 /^[\d][\d][\d][\d][\d][\d][\d][\d][\d][\d][\d][\d]/ 123456654321 /^[abc]{12}/ abcabcabcabc /^[a-c]{12}/ abcabcabcabc /^(a|b|c){12}/ abcabcabcabc /^[abcdefghijklmnopqrstuvwxy0123456789]/ n *** Failers z /abcde{0,0}/ abcd *** Failers abce /ab[cd]{0,0}e/ abe *** Failers abcde /ab(c){0,0}d/ abd *** Failers abcd /a(b*)/ a ab abbbb *** Failers bbbbb /ab\d{0}e/ abe *** Failers ab1e /"([^\\"]+|\\.)*"/ the \"quick\" brown fox \"the \\\"quick\\\" brown fox\" /.*?/g+ abc /\b/g+ abc /\b/+g abc / /g abc /a[^a]b/ acb a\nb /a.b/ acb *** Failers a\nb /a[^a]b/s acb a\nb /a.b/s acb a\nb /^(b+?|a){1,2}?c/ bac bbac bbbac bbbbac bbbbbac /^(b+|a){1,2}?c/ bac bbac bbbac bbbbac bbbbbac /(?!\A)x/m x\nb\n a\bx\n /\x0{ab}/ \0{ab} /(A|B)*?CD/ CD /(A|B)*CD/ CD /(AB)*?\1/ ABABAB /(AB)*\1/ ABABAB /(?.*/)foo" /this/is/a/very/long/line/in/deed/with/very/many/slashes/in/it/you/see/ "(?>.*/)foo" /this/is/a/very/long/line/in/deed/with/very/many/slashes/in/and/foo /(?>(\.\d\d[1-9]?))\d+/ 1.230003938 1.875000282 *** Failers 1.235 /^((?>\w+)|(?>\s+))*$/ now is the time for all good men to come to the aid of the party *** Failers this is not a line with only words and spaces! /(\d+)(\w)/ 12345a 12345+ /((?>\d+))(\w)/ 12345a *** Failers 12345+ /(?>a+)b/ aaab /((?>a+)b)/ aaab /(?>(a+))b/ aaab /(?>b)+/ aaabbbccc /(?>a+|b+|c+)*c/ aaabbbbccccd /((?>[^()]+)|\([^()]*\))+/ ((abc(ade)ufh()()x /\(((?>[^()]+)|\([^()]+\))+\)/ (abc) (abc(def)xyz) *** Failers ((()aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa /a(?-i)b/i ab Ab *** Failers aB AB /(a (?x)b c)d e/ a bcd e *** Failers a b cd e abcd e a bcde /(a b(?x)c d (?-x)e f)/ a bcde f *** Failers abcdef /(a(?i)b)c/ abc aBc *** Failers abC aBC Abc ABc ABC AbC /a(?i:b)c/ abc aBc *** Failers ABC abC aBC /a(?i:b)*c/ aBc aBBc *** Failers aBC aBBC /a(?=b(?i)c)\w\wd/ abcd abCd *** Failers aBCd abcD /(?s-i:more.*than).*million/i more than million more than MILLION more \n than Million *** Failers MORE THAN MILLION more \n than \n million /(?:(?s-i)more.*than).*million/i more than million more than MILLION more \n than Million *** Failers MORE THAN MILLION more \n than \n million /(?>a(?i)b+)+c/ abc aBbc aBBc *** Failers Abc abAb abbC /(?=a(?i)b)\w\wc/ abc aBc *** Failers Ab abC aBC /(?<=a(?i)b)(\w\w)c/ abxxc aBxxc *** Failers Abxxc ABxxc abxxC /(?:(a)|b)(?(1)A|B)/ aA bB *** Failers aB bA /^(a)?(?(1)a|b)+$/ aa b bb *** Failers ab /^(?(?=abc)\w{3}:|\d\d)$/ abc: 12 *** Failers 123 xyz /^(?(?!abc)\d\d|\w{3}:)$/ abc: 12 *** Failers 123 xyz /(?(?<=foo)bar|cat)/ foobar cat fcat focat *** Failers foocat /(?(?a*)*/ a aa aaaa /(abc|)+/ abc abcabc abcabcabc xyz /([a]*)*/ a aaaaa /([ab]*)*/ a b ababab aaaabcde bbbb /([^a]*)*/ b bbbb aaa /([^ab]*)*/ cccc abab /([a]*?)*/ a aaaa /([ab]*?)*/ a b abab baba /([^a]*?)*/ b bbbb aaa /([^ab]*?)*/ c cccc baba /(?>a*)*/ a aaabcde /((?>a*))*/ aaaaa aabbaa /((?>a*?))*/ aaaaa aabbaa /(?(?=[^a-z]+[a-z]) \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) /x 12-sep-98 12-09-98 *** Failers sep-12-98 /(?<=(foo))bar\1/ foobarfoo foobarfootling *** Failers foobar barfoo /(?i:saturday|sunday)/ saturday sunday Saturday Sunday SATURDAY SUNDAY SunDay /(a(?i)bc|BB)x/ abcx aBCx bbx BBx *** Failers abcX aBCX bbX BBX /^([ab](?i)[cd]|[ef])/ ac aC bD elephant Europe frog France *** Failers Africa /^(ab|a(?i)[b-c](?m-i)d|x(?i)y|z)/ ab aBd xy xY zebra Zambesi *** Failers aCD XY /(?<=foo\n)^bar/m foo\nbar *** Failers bar baz\nbar /(?<=(?]&/ <&OUT /^(a\1?){4}$/ aaaaaaaaaa *** Failers AB aaaaaaaaa aaaaaaaaaaa /^(a(?(1)\1)){4}$/ aaaaaaaaaa *** Failers aaaaaaaaa aaaaaaaaaaa /(?:(f)(o)(o)|(b)(a)(r))*/ foobar /(?<=a)b/ ab *** Failers cb b /(?a+)ab/ /(?>a+)b/ aaab /([[:]+)/ a:[b]: /([[=]+)/ a=[b]= /([[.]+)/ a.[b]. /((?>a+)b)/ aaab /(?>(a+))b/ aaab /((?>[^()]+)|\([^()]*\))+/ ((abc(ade)ufh()()x /a\Z/ *** Failers aaab a\nb\n /b\Z/ a\nb\n /b\z/ /b\Z/ a\nb /b\z/ a\nb *** Failers /^(?>(?(1)\.|())[^\W_](?>[a-z0-9-]*[^\W_])?)+$/ a abc a-b 0-9 a.b 5.6.7 the.quick.brown.fox a100.b200.300c 12-ab.1245 *** Failers \ .a -a a- a. a_b a.- a.. ab..bc the.quick.brown.fox- the.quick.brown.fox. the.quick.brown.fox_ the.quick.brown.fox+ /(?>.*)(?<=(abcd|wxyz))/ alphabetabcd endingwxyz *** Failers a rather long string that doesn't end with one of them /word (?>(?:(?!otherword)[a-zA-Z0-9]+ ){0,30})otherword/ word cat dog elephant mussel cow horse canary baboon snake shark otherword word cat dog elephant mussel cow horse canary baboon snake shark /word (?>[a-zA-Z0-9]+ ){0,30}otherword/ word cat dog elephant mussel cow horse canary baboon snake shark the quick brown fox and the lazy dog and several other words getting close to thirty by now I hope /(?<=\d{3}(?!999))foo/ 999foo 123999foo *** Failers 123abcfoo /(?<=(?!...999)\d{3})foo/ 999foo 123999foo *** Failers 123abcfoo /(?<=\d{3}(?!999)...)foo/ 123abcfoo 123456foo *** Failers 123999foo /(?<=\d{3}...)(?Z)+|A)*/ ZABCDEFG /((?>)+|A)*/ ZABCDEFG /a*/g abbab /^[a-d]/ abcde -things 0digit *** Failers bcdef /^[\d-a]/ abcde -things 0digit *** Failers bcdef /[[:space:]]+/ > \x09\x0a\x0c\x0d\x0b< /[[:blank:]]+/ > \x09\x0a\x0c\x0d\x0b< /[\s]+/ > \x09\x0a\x0c\x0d\x0b< /\s+/ > \x09\x0a\x0c\x0d\x0b< /a b/x ab /(?!\A)x/m a\nxb\n /(?!^)x/m a\nxb\n /abc\Qabc\Eabc/ abcabcabc / abc\Q abc\Eabc/x abc abcabc *** Failers abcabcabc /\Qabc\$xyz\E/ abc\\\$xyz /\Qabc\E\$\Qxyz\E/ abc\$xyz /\Gabc/ abc *** Failers xyzabc /\Gabc./g abc1abc2xyzabc3 /abc./g abc1abc2xyzabc3 /a(?x: b c )d/ XabcdY *** Failers Xa b c d Y /((?x)x y z | a b c)/ XabcY AxyzB /(?i)AB(?-i)C/ XabCY *** Failers XabcY /((?i)AB(?-i)C|D)E/ abCE DE *** Failers abcE abCe dE De /(.*)\d+\1/ abc123abc abc123bc /(.*)\d+\1/s abc123abc abc123bc /((.*))\d+\1/ abc123abc abc123bc /[z\Qa-d]\E]/ z a - d ] *** Failers b /[\z\C]/ z C /\M/ M /(a+)*b/ aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa /(?i)reg(?:ul(?:[a]|ae)r|ex)/ REGular regulaer Regex regulr /[--]+/ /(?<=Z)X./ \x84XAZXB