diff --git a/basis/regexp/classes/classes-tests.factor b/basis/regexp/classes/classes-tests.factor
index 9a210fb576..520e23c749 100644
--- a/basis/regexp/classes/classes-tests.factor
+++ b/basis/regexp/classes/classes-tests.factor
@@ -30,6 +30,7 @@ IN: regexp.classes.tests
 [ T{ or-class { seq { 3 2 } } } ] [ { 2 3 } <or-class> 1 <not-class> 2array <and-class> ] unit-test
 [ f ] [ t <not-class> ] unit-test
 [ t ] [ f <not-class> ] unit-test
+[ f ] [ 1 <not-class> 1 t replace-question ] unit-test
 
 ! Making classes into nested conditionals
 
@@ -43,7 +44,7 @@ IN: regexp.classes.tests
 SYMBOL: foo
 SYMBOL: bar
 
-[ T{ condition f T{ primitive-class f bar } T{ condition f T{ primitive-class f foo } { 1 2 3 } { 1 3 } } T{ condition f T{ primitive-class f foo } { 1 2 } { 1 } } } ] [ { { 1 t } { 2 T{ primitive-class f foo } } { 3 T{ primitive-class f bar } } } table>condition ] unit-test
+[ T{ condition f T{ primitive-class f bar } T{ condition f T{ primitive-class f foo } { 1 3 2 } { 1 3 } } T{ condition f T{ primitive-class f foo } { 1 2 } { 1 } } } ] [ { { 1 t } { 3 T{ primitive-class f bar } } { 2 T{ primitive-class f foo } } } table>condition ] unit-test
 
 [ t ] [ foo <primitive-class> dup t replace-question ] unit-test
 [ f ] [ foo <primitive-class> dup f replace-question ] unit-test
diff --git a/basis/regexp/classes/classes.factor b/basis/regexp/classes/classes.factor
index f8fce02213..6ea87fbb49 100644
--- a/basis/regexp/classes/classes.factor
+++ b/basis/regexp/classes/classes.factor
@@ -12,7 +12,7 @@ ascii-class punctuation-class java-printable-class blank-class
 control-character-class hex-digit-class java-blank-class c-identifier-class
 unmatchable-class terminator-class word-boundary-class ;
 
-SINGLETONS: beginning-of-input ^ end-of-input $ ;
+SINGLETONS: beginning-of-input ^ end-of-input $ end-of-file ;
 
 TUPLE: range from to ;
 C: <range> range
@@ -233,7 +233,7 @@ M: or-class replace-question
     replace-compound <or-class> ;
 
 M: not-class replace-question
-    class>> replace-question <not-class> ;
+    [ class>> ] 2dip replace-question <not-class> ;
 
 : answer ( table question answer -- new-table )
     '[ _ _ replace-question ] assoc-map
@@ -258,7 +258,7 @@ M: not-class class>questions class>> class>questions ;
 M: object class>questions 1array ;
 
 : table>questions ( table -- questions )
-    values <and-class> class>questions t swap remove ;
+    values [ class>questions ] gather >array t swap remove ;
 
 : table>condition ( table -- condition )
     ! input table is state => class
@@ -269,3 +269,12 @@ M: object class>questions 1array ;
         [ [ question>> ] [ yes>> ] [ no>> ] tri ] dip
         '[ _ condition-map ] bi@ <condition>
     ] [ call ] if ; inline recursive
+
+: condition-states ( condition -- states )
+    dup condition? [
+        [ yes>> ] [ no>> ] bi
+        [ condition-states ] bi@ append prune
+    ] [ 1array ] if ;
+
+: condition-at ( condition assoc -- new-condition )
+    '[ _ at ] condition-map ;
diff --git a/basis/regexp/compiler/compiler.factor b/basis/regexp/compiler/compiler.factor
index 30c9a5a5cb..d0f60fc6a2 100644
--- a/basis/regexp/compiler/compiler.factor
+++ b/basis/regexp/compiler/compiler.factor
@@ -3,27 +3,76 @@
 USING: regexp.classes kernel sequences regexp.negation
 quotations regexp.minimize assocs fry math locals combinators
 accessors words compiler.units kernel.private strings
-sequences.private arrays regexp.matchers call ;
+sequences.private arrays regexp.matchers call namespaces
+regexp.transition-tables combinators.short-circuit ;
 IN: regexp.compiler
 
-: literals>cases ( literal-transitions -- case-body )
-    [ 1quotation ] assoc-map ;
+GENERIC: question>quot ( question -- quot )
+
+<PRIVATE
+
+SYMBOL: shortest?
+SYMBOL: backwards?
+
+M: t question>quot drop [ 2drop t ] ;
+
+M: beginning-of-input question>quot
+    drop [ drop zero? ] ;
+
+M: end-of-input question>quot
+    drop [ length = ] ;
+
+M: end-of-file question>quot
+    drop [
+        {
+            [ length swap - 2 <= ]
+            [ swap tail { "\n" "\r\n" "\r" "" } member? ]
+        } 2&&
+        [ [ nip [ length ] keep ] when ] keep
+    ] ;
+
+M: $ question>quot
+    drop [ { [ length = ] [ ?nth "\r\n" member? ] } 2|| ] ;
+
+M: ^ question>quot
+    drop [ { [ drop zero? ] [ [ 1- ] dip ?nth "\r\n" member? ] } 2|| ] ;
+
+! Maybe the condition>quot things can be combined, given a suitable method
+! for question>quot on classes, but maybe that'd make stack shuffling annoying
+
+: execution-quot ( next-state -- quot )
+    ! The conditions here are for lookaround and anchors, etc
+    dup condition? [
+        [ question>> question>quot ] [ yes>> ] [ no>> ] tri
+        [ execution-quot ] bi@
+        '[ 2dup @ _ _ if ]
+    ] [
+        ! There shouldn't be a condition like this!
+        dup sequence?
+        [ [ [ 2drop ] ] [ first '[ _ execute ] ] if-empty ]
+        [ '[ _ execute ] ] if
+    ] if ;
+
+TUPLE: box contents ;
+C: <box> box
 
 : condition>quot ( condition -- quot )
+    ! Conditions here are for different classes
     dup condition? [
         [ question>> ] [ yes>> ] [ no>> ] tri
         [ condition>quot ] bi@
         '[ dup _ class-member? _ _ if ]
     ] [
-        [ [ 3drop ] ] [ '[ drop _ execute ] ] if-empty
+        contents>>
+        [ [ 3drop ] ] [ execution-quot '[ drop @ ] ] if-empty
     ] if ;
 
-: new-non-literals>dispatch ( non-literal-transitions -- quot )
-    table>condition condition>quot ;
-
 : non-literals>dispatch ( non-literal-transitions -- quot )
-    [ [ '[ dup _ class-member? ] ] [ '[ drop _ execute ] ] bi* ] assoc-map
-    [ 3drop ] suffix '[ _ cond ] ;
+    [ swap ] assoc-map ! we want state => predicate, and get the opposite as input
+    table>condition [ <box> ] condition-map condition>quot ;
+
+: literals>cases ( literal-transitions -- case-body )
+    [ execution-quot ] assoc-map ;
 
 : expand-one-or ( or-class transition -- alist )
     [ seq>> ] dip '[ _ 2array ] map ;
@@ -38,17 +87,22 @@ IN: regexp.compiler
     >alist expand-or [ first integer? ] partition
     [ literals>cases ] [ non-literals>dispatch ] bi* ;
 
-:: step ( last-match index str case-body final? -- last-index/f )
+:: step ( last-match index str quot final? direction -- last-index/f )
     final? index last-match ?
     index str bounds-check? [
-        index 1+ str
+        index direction + str
         index str nth-unsafe
-        case-body case
+        quot call
     ] when ; inline
 
+: direction ( -- n )
+    backwards? get -1 1 ? ;
+
 : transitions>quot ( transitions final-state? -- quot )
-    [ split-literals suffix ] dip
-    '[ { array-capacity sequence } declare _ _ step ] ;
+    dup shortest? get and [ 2drop [ drop nip ] ] [
+        [ split-literals swap case>quot ] dip direction
+        '[ { array-capacity string } declare _ _ _ step ]
+    ] if ;
 
 : word>quot ( word dfa -- quot )
     [ transitions>> at ]
@@ -64,30 +118,37 @@ IN: regexp.compiler
         ] each
     ] with-compilation-unit ;
 
-: transitions-at ( transitions assoc -- new-transitions )
-    dup '[
-        [ _ at ]
-        [ [ _ at ] assoc-map ] bi*
-    ] assoc-map ;
-
 : states>words ( dfa -- words dfa )
     dup transitions>> keys [ gensym ] H{ } map>assoc
-    [ [ transitions-at ] rewrite-transitions ]
+    [ transitions-at ]
     [ values ]
     bi swap ; 
 
 : dfa>word ( dfa -- word )
     states>words [ states>code ] keep start-state>> ;
 
-: check-sequence ( string -- string )
+: check-string ( string -- string )
     ! Make this configurable
-    dup sequence? [ "String required" throw ] unless ;
+    dup string? [ "String required" throw ] unless ;
 
-: run-regexp ( start-index string word -- ? )
-    { [ f ] [ >fixnum ] [ check-sequence ] [ execute ] } spread ; inline
+: setup-regexp ( start-index string -- f start-index string )
+    [ f ] [ >fixnum ] [ check-string ] tri* ; inline
+
+PRIVATE>
+
+! The quotation returned is ( start-index string -- i/f )
 
 : dfa>quotation ( dfa -- quot )
-    dfa>word '[ _ run-regexp ] ;
+    dfa>word execution-quot '[ setup-regexp @ ] ;
+
+: dfa>shortest-quotation ( dfa -- quot )
+    t shortest? [ dfa>quotation ] with-variable ;
+
+: dfa>reverse-quotation ( dfa -- quot )
+    t backwards? [ dfa>quotation ] with-variable ;
+
+: dfa>reverse-shortest-quotation ( dfa -- quot )
+    t backwards? [ dfa>shortest-quotation ] with-variable ;
 
 TUPLE: quot-matcher quot ;
 C: <quot-matcher> quot-matcher
diff --git a/basis/regexp/dfa/dfa.factor b/basis/regexp/dfa/dfa.factor
index 6ddc0396a7..d137ee3e4f 100644
--- a/basis/regexp/dfa/dfa.factor
+++ b/basis/regexp/dfa/dfa.factor
@@ -39,21 +39,26 @@ IN: regexp.dfa
 
 : find-transitions ( dfa-state nfa -- next-dfa-state )
     transitions>>
-    '[ _ at keys ] gather
-    epsilon swap remove ;
+    '[ _ at keys [ condition-states ] map concat ] gather
+    [ tagged-epsilon? not ] filter ;
 
 : add-todo-state ( state visited-states new-states -- )
     3dup drop key? [ 3drop ] [
         [ conjoin ] [ push ] bi-curry* bi
     ] if ;
 
+: add-todo-states ( state/condition visited-states new-states -- )
+    [ condition-states ] 2dip
+    '[ _ _ add-todo-state ] each ;
+
 :: new-transitions ( nfa dfa new-states visited-states -- nfa dfa )
     new-states [ nfa dfa ] [
         pop :> state
+        state dfa transitions>> maybe-initialize-key
         state nfa find-transitions
         [| trans |
             state trans nfa find-closure :> new-state
-            new-state visited-states new-states add-todo-state
+            new-state visited-states new-states add-todo-states
             state new-state trans dfa set-transition
         ] each
         nfa dfa new-states visited-states new-transitions
@@ -73,7 +78,7 @@ IN: regexp.dfa
 
 : construct-dfa ( nfa -- dfa )
     dup initialize-dfa
-    dup start-state>> 1vector
+    dup start-state>> condition-states >vector
     H{ } clone
     new-transitions
     [ set-final-states ] keep ;
diff --git a/basis/regexp/disambiguate/disambiguate.factor b/basis/regexp/disambiguate/disambiguate.factor
index abfe76d832..eac9c7e81d 100644
--- a/basis/regexp/disambiguate/disambiguate.factor
+++ b/basis/regexp/disambiguate/disambiguate.factor
@@ -42,6 +42,3 @@ TUPLE: parts in out ;
             ] preserving-epsilon
         ] assoc-map
     ] change-transitions ;
-
-: nfa>dfa ( nfa -- dfa )
-    disambiguate construct-dfa minimize ;
diff --git a/basis/regexp/minimize/minimize.factor b/basis/regexp/minimize/minimize.factor
index c98cf131cb..822ca68caf 100644
--- a/basis/regexp/minimize/minimize.factor
+++ b/basis/regexp/minimize/minimize.factor
@@ -5,29 +5,11 @@ accessors locals math sorting arrays sets hashtables regexp.dfa
 combinators.short-circuit regexp.classes ;
 IN: regexp.minimize
 
-: number-transitions ( transitions numbering -- new-transitions )
-    dup '[
-        [ _ at ]
-        [ [ [ _ at ] condition-map ] assoc-map ] bi*
-    ] assoc-map ;
-
 : table>state-numbers ( table -- assoc )
     transitions>> keys <enum> [ swap ] H{ } assoc-map-as ;
 
-: map-set ( assoc quot -- new-assoc )
-    '[ drop @ dup ] assoc-map ; inline
-
-: rewrite-transitions ( transition-table assoc quot -- transition-table )
-    [
-        [ clone ] dip
-        [ '[ _ at ] change-start-state ]
-        [ '[ [ _ at ] map-set ] change-final-states ]
-        [ ] tri
-    ] dip '[ _ @ ] change-transitions ; inline
-
 : number-states ( table -- newtable )
-    dup table>state-numbers
-    [ number-transitions ] rewrite-transitions ;
+    dup table>state-numbers transitions-at ;
 
 : no-conditions? ( state transition-table -- ? )
     transitions>> at values [ condition? ] any? not ;
@@ -103,4 +85,4 @@ IN: regexp.minimize
     [ combine-transitions ] rewrite-transitions ;
 
 : minimize ( table -- minimal-table )
-    clone number-states combine-states ;
+    clone number-states ; ! combine-states ;
diff --git a/basis/regexp/negation/negation.factor b/basis/regexp/negation/negation.factor
index 0cfcdfc6ea..b03223fabf 100644
--- a/basis/regexp/negation/negation.factor
+++ b/basis/regexp/negation/negation.factor
@@ -2,11 +2,12 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: regexp.nfa regexp.disambiguate kernel sequences
 assocs regexp.classes hashtables accessors fry vectors
-regexp.ast regexp.transition-tables regexp.minimize namespaces ;
+regexp.ast regexp.transition-tables regexp.minimize
+regexp.dfa namespaces ;
 IN: regexp.negation
 
 : ast>dfa ( parse-tree -- minimal-dfa )
-    construct-nfa nfa>dfa ;
+    construct-nfa disambiguate construct-dfa minimize ;
 
 CONSTANT: fail-state -1
 
@@ -33,15 +34,9 @@ CONSTANT: fail-state -1
         [ add-fail-state ] change-transitions
         dup inverse-final-states >>final-states ;
 
-: renumber-transitions ( transitions numbering -- new-transitions )
-    dup '[
-        [ _ at ]
-        [ [ [ _ at ] map ] assoc-map ] bi*
-    ] assoc-map ;
-
 : renumber-states ( transition-table -- transition-table )
     dup transitions>> keys [ next-state ] H{ } map>assoc
-    [ renumber-transitions ] rewrite-transitions ;
+    transitions-at ;
 
 : box-transitions ( transition-table -- transition-table )
     [ [ [ 1vector ] assoc-map ] assoc-map ] change-transitions ;
diff --git a/basis/regexp/nfa/nfa.factor b/basis/regexp/nfa/nfa.factor
index 302b1ebc55..2dc2c1798b 100644
--- a/basis/regexp/nfa/nfa.factor
+++ b/basis/regexp/nfa/nfa.factor
@@ -56,9 +56,16 @@ M:: star nfa-node ( node -- start end )
     s2 s3 ;
 
 GENERIC: modify-epsilon ( tag -- newtag )
+! Potential off-by-one errors when lookaround nested in lookbehind
 
 M: object modify-epsilon ;
 
+M: $ modify-epsilon
+    multiline option? [ drop end-of-input ] unless ;
+
+M: ^ modify-epsilon
+    multiline option? [ drop beginning-of-input ] unless ;
+
 M: tagged-epsilon nfa-node
     clone [ modify-epsilon ] change-tag add-simple-entry ;
 
diff --git a/basis/regexp/parser/parser.factor b/basis/regexp/parser/parser.factor
index 18aef7fa49..5870395b7c 100644
--- a/basis/regexp/parser/parser.factor
+++ b/basis/regexp/parser/parser.factor
@@ -54,6 +54,7 @@ ERROR: bad-class name ;
         { CHAR: D [ digit-class <primitive-class> <not-class> ] }
 
         { CHAR: z [ end-of-input <tagged-epsilon> ] }
+        { CHAR: Z [ end-of-file <tagged-epsilon> ] }
         { CHAR: A [ beginning-of-input <tagged-epsilon> ] }
         [ ]
     } case ;
diff --git a/basis/regexp/regexp-tests.factor b/basis/regexp/regexp-tests.factor
index 9425e38727..488ab8cba3 100644
--- a/basis/regexp/regexp-tests.factor
+++ b/basis/regexp/regexp-tests.factor
@@ -45,9 +45,9 @@ IN: regexp-tests
 ! Dotall mode -- when on, . matches newlines.
 ! Off by default.
 [ f ] [ "\n" "." <regexp> matches? ] unit-test
-! [ t ] [ "\n" "(?s)." <regexp> matches? ] unit-test
+[ t ] [ "\n" "(?s:.)" <regexp> matches? ] unit-test
 [ t ] [ "\n" R/ ./s matches? ] unit-test
-! [ f ] [ "\n\n" "(?s).(?-s)." <regexp> matches? ] unit-test
+[ f ] [ "\n\n" "(?s:.)." <regexp> matches? ] unit-test
 
 [ f ] [ "" ".+" <regexp> matches? ] unit-test
 [ t ] [ "a" ".+" <regexp> matches? ] unit-test
@@ -221,17 +221,15 @@ IN: regexp-tests
 [ t ] [ "c" R/ [A-Z]/i matches? ] unit-test
 [ f ] [ "3" R/ [A-Z]/i matches? ] unit-test
 
-/*
-[ t ] [ "a" "(?i)a" <regexp> matches? ] unit-test
-[ t ] [ "a" "(?i)a" <regexp> matches? ] unit-test
-[ t ] [ "A" "(?i)a" <regexp> matches? ] unit-test
-[ t ] [ "A" "(?i)a" <regexp> matches? ] unit-test
+[ t ] [ "a" "(?i:a)" <regexp> matches? ] unit-test
+[ t ] [ "a" "(?i:a)" <regexp> matches? ] unit-test
+[ t ] [ "A" "(?i:a)" <regexp> matches? ] unit-test
+[ t ] [ "A" "(?i:a)" <regexp> matches? ] unit-test
 
-[ t ] [ "a" R/ (?-i)a/i matches? ] unit-test
-[ t ] [ "a" R/ (?-i)a/i matches? ] unit-test
-[ f ] [ "A" R/ (?-i)a/i matches? ] unit-test
-[ f ] [ "A" R/ (?-i)a/i matches? ] unit-test
-*/
+[ t ] [ "a" R/ (?-i:a)/i matches? ] unit-test
+[ t ] [ "a" R/ (?-i:a)/i matches? ] unit-test
+[ f ] [ "A" R/ (?-i:a)/i matches? ] unit-test
+[ f ] [ "A" R/ (?-i:a)/i matches? ] unit-test
 
 [ f ] [ "A" "[a-z]" <regexp> matches? ] unit-test
 [ t ] [ "A" R/ [a-z]/i matches? ] unit-test
@@ -242,8 +240,8 @@ IN: regexp-tests
 [ t ] [ "abc" reverse R/ abc/r matches? ] unit-test
 [ t ] [ "abc" reverse R/ a[bB][cC]/r matches? ] unit-test
 
-[ t ] [ "xabc" R/ abc/ <reverse-matcher> match-index-head >boolean ] unit-test
-[ t ] [ "xabc" R/ a[bB][cC]/ <reverse-matcher> match-index-head >boolean ] unit-test
+[ t ] [ 3 "xabc" R/ abc/ <reverse-matcher> match-index-from >boolean ] unit-test
+[ t ] [ 3 "xabc" R/ a[bB][cC]/ <reverse-matcher> match-index-from >boolean ] unit-test
 
 [ t ] [ "s@f" "[a-z.-]@[a-z]" <regexp> matches? ] unit-test
 [ f ] [ "a" "[a-z.-]@[a-z]" <regexp> matches? ] unit-test
@@ -276,10 +274,6 @@ IN: regexp-tests
 
 [ "b" ] [ "aaaaaaaaaaaaaaaaaaaaaaab" "((a*)*b)*b" <regexp> match-head >string ] unit-test
 
-! [ t ] [ "a:b" ".+:?" <regexp> matches? ] unit-test
-
-! [ 1 ] [ "hello" ".+?" <regexp> match length ] unit-test
-
 [ { "1" "2" "3" "4" } ]
 [ "1ABC2DEF3GHI4" R/ [A-Z]+/ re-split [ >string ] map ] unit-test
 
@@ -304,18 +298,16 @@ IN: regexp-tests
   
 [ "-- title --" ] [ "== title ==" R/ =/ "-" re-replace ] unit-test
 
-/*
 [ f ] [ "ab" "a(?!b)" <regexp> match-head ] unit-test
 [ "a" ] [ "ac" "a(?!b)" <regexp> match-head >string ] unit-test
 [ t ] [ "fxxbar" "(?!foo).{3}bar" <regexp> matches? ] unit-test
 [ f ] [ "foobar" "(?!foo).{3}bar" <regexp> matches? ] unit-test
 [ "a" ] [ "ab" "a(?=b)(?=b)" <regexp> match-head >string ] unit-test
-[ "a" ] [ "ba" "a(?<=b)(?<=b)" <regexp> match-head >string ] unit-test
-[ "a" ] [ "cab" "a(?=b)(?<=c)" <regexp> match-head >string ] unit-test
+[ "a" ] [ "ba" "(?<=b)(?<=b)a" <regexp> match-head >string ] unit-test
+[ "a" ] [ "cab" "(?<=c)a(?=b)" <regexp> match-head >string ] unit-test
 
 [ 3 ] [ "foobar" "foo(?=bar)" <regexp> match-index-head ] unit-test
 [ f ] [ "foobxr" "foo(?=bar)" <regexp> match-index-head ] unit-test
-*/
 
 ! Bug in parsing word
 [ t ] [ "a" R' a' matches? ] unit-test
@@ -349,56 +341,70 @@ IN: regexp-tests
 [ f ] [ "foo" <regexp> dfa>> >boolean ] unit-test
 [ t ] [ R/ foo/ dfa>> >boolean ] unit-test
 
-! [ t ] [ "a" R/ ^a/ matches? ] unit-test
-! [ f ] [ "\na" R/ ^a/ matches? ] unit-test
-! [ f ] [ "\r\na" R/ ^a/ matches? ] unit-test
-! [ f ] [ "\ra" R/ ^a/ matches? ] unit-test
+[ t ] [ "a" R/ ^a/ matches? ] unit-test
+[ f ] [ "\na" R/ ^a/ matches? ] unit-test
+[ f ] [ "\r\na" R/ ^a/ matches? ] unit-test
+[ f ] [ "\ra" R/ ^a/ matches? ] unit-test
 
-! [ t ] [ "a" R/ a$/ matches? ] unit-test
-! [ f ] [ "a\n" R/ a$/ matches? ] unit-test
-! [ f ] [ "a\r" R/ a$/ matches? ] unit-test
-! [ f ] [ "a\r\n" R/ a$/ matches? ] unit-test
+[ 1 ] [ "a" R/ ^a/ count-matches ] unit-test
+[ 0 ] [ "\na" R/ ^a/ count-matches ] unit-test
+[ 0 ] [ "\r\na" R/ ^a/ count-matches ] unit-test
+[ 0 ] [ "\ra" R/ ^a/ count-matches ] unit-test
 
-! [ t ] [ "a" R/ a$|b$/ matches? ] unit-test
-! [ t ] [ "b" R/ a$|b$/ matches? ] unit-test
-! [ t ] [ "ab" R/ a$|b$/ matches? ] unit-test
-! [ t ] [ "ba" R/ ba$|b$/ matches? ] unit-test
+[ t ] [ "a" R/ a$/ matches? ] unit-test
+[ f ] [ "a\n" R/ a$/ matches? ] unit-test
+[ f ] [ "a\r" R/ a$/ matches? ] unit-test
+[ f ] [ "a\r\n" R/ a$/ matches? ] unit-test
 
-! [ t ] [ "a" R/ \Aa/ matches? ] unit-test
-! [ f ] [ "\na" R/ \Aaa/ matches? ] unit-test
-! [ f ] [ "\r\na" R/ \Aa/ matches? ] unit-test
-! [ f ] [ "\ra" R/ \Aa/ matches? ] unit-test
+[ 1 ] [ "a" R/ a$/ count-matches ] unit-test
+[ 0 ] [ "a\n" R/ a$/ count-matches ] unit-test
+[ 0 ] [ "a\r" R/ a$/ count-matches ] unit-test
+[ 0 ] [ "a\r\n" R/ a$/ count-matches ] unit-test
 
-! [ t ] [ "a" R/ \Aa/m matches? ] unit-test
-! [ f ] [ "\na" R/ \Aaa/m matches? ] unit-test
-! [ f ] [ "\r\na" R/ \Aa/m matches? ] unit-test
-! [ f ] [ "\ra" R/ \Aa/m matches? ] unit-test
+[ t ] [ "a" R/ a$|b$/ matches? ] unit-test
+[ t ] [ "b" R/ a$|b$/ matches? ] unit-test
+[ f ] [ "ab" R/ a$|b$/ matches? ] unit-test
+[ t ] [ "ba" R/ ba$|b$/ matches? ] unit-test
 
-! [ t ] [ "\r\n\n\n\nam" R/ ^am/m matches? ] unit-test
+[ t ] [ "a" R/ \Aa/ matches? ] unit-test
+[ f ] [ "\na" R/ \Aaa/ matches? ] unit-test
+[ f ] [ "\r\na" R/ \Aa/ matches? ] unit-test
+[ f ] [ "\ra" R/ \Aa/ matches? ] unit-test
 
-! [ t ] [ "a" R/ \Aa\z/m matches? ] unit-test
-! [ f ] [ "a\n" R/ \Aa\z/m matches? ] unit-test
+[ t ] [ "a" R/ \Aa/m matches? ] unit-test
+[ f ] [ "\na" R/ \Aaa/m matches? ] unit-test
+[ f ] [ "\r\na" R/ \Aa/m matches? ] unit-test
+[ f ] [ "\ra" R/ \Aa/m matches? ] unit-test
+[ 0 ] [ "\ra" R/ \Aa/m count-matches ] unit-test
 
-! [ t ] [ "a\r\n" R/ \Aa\Z/m matches? ] unit-test
-! [ t ] [ "a\n" R/ \Aa\Z/m matches? ] unit-test
+[ f ] [ "\r\n\n\n\nam" R/ ^am/m matches? ] unit-test
+[ 1 ] [ "\r\n\n\n\nam" R/ ^am/m count-matches ] unit-test
 
-! [ t ] [ "a" R/ \Aa\Z/m matches? ] unit-test
-! [ f ] [ "\na" R/ \Aaa\Z/m matches? ] unit-test
-! [ f ] [ "\r\na" R/ \Aa\Z/m matches? ] unit-test
-! [ f ] [ "\ra" R/ \Aa\Z/m matches? ] unit-test
+[ t ] [ "a" R/ \Aa\z/m matches? ] unit-test
+[ f ] [ "a\n" R/ \Aa\z/m matches? ] unit-test
 
-! [ t ] [ "a" R/ ^a/m matches? ] unit-test
-! [ t ] [ "\na" R/ ^a/m matches? ] unit-test
-! [ t ] [ "\r\na" R/ ^a/m matches? ] unit-test
-! [ t ] [ "\ra" R/ ^a/m matches? ] unit-test
+[ t ] [ "a\r\n" R/ \Aa\Z/m matches? ] unit-test
+[ t ] [ "a\n" R/ \Aa\Z/m matches? ] unit-test
 
-! [ t ] [ "a" R/ a$/m matches? ] unit-test
-! [ t ] [ "a\n" R/ a$/m matches? ] unit-test
-! [ t ] [ "a\r" R/ a$/m matches? ] unit-test
-! [ t ] [ "a\r\n" R/ a$/m matches? ] unit-test
+[ t ] [ "a" R/ \Aa\Z/m matches? ] unit-test
+[ f ] [ "\na" R/ \Aaa\Z/m matches? ] unit-test
+[ f ] [ "\r\na" R/ \Aa\Z/m matches? ] unit-test
+[ f ] [ "\ra" R/ \Aa\Z/m matches? ] unit-test
 
-! [ f ] [ "foobxr" "foo\\z" <regexp> match-index-head ] unit-test
-! [ 3 ] [ "foo" "foo\\z" <regexp> match-index-head ] unit-test
+[ t ] [ "a" R/ ^a/m matches? ] unit-test
+[ f ] [ "\na" R/ ^a/m matches? ] unit-test
+[ 1 ] [ "\na" R/ ^a/m count-matches ] unit-test
+[ 1 ] [ "\r\na" R/ ^a/m count-matches ] unit-test
+[ 1 ] [ "\ra" R/ ^a/m count-matches ] unit-test
+
+[ t ] [ "a" R/ a$/m matches? ] unit-test
+[ f ] [ "a\n" R/ a$/m matches? ] unit-test
+[ 1 ] [ "a\n" R/ a$/m count-matches ] unit-test
+[ 1 ] [ "a\r" R/ a$/m count-matches ] unit-test
+[ 1 ] [ "a\r\n" R/ a$/m count-matches ] unit-test
+
+[ f ] [ "foobxr" "foo\\z" <regexp> match-index-head ] unit-test
+[ 3 ] [ "foo" "foo\\z" <regexp> match-index-head ] unit-test
 
 ! [ t ] [ "foo" "\\bfoo\\b" <regexp> matches? ] unit-test
 ! [ t ] [ "afoob" "\\Bfoo\\B" <regexp> matches? ] unit-test
diff --git a/basis/regexp/regexp.factor b/basis/regexp/regexp.factor
index 1bd242315f..6693691ba8 100644
--- a/basis/regexp/regexp.factor
+++ b/basis/regexp/regexp.factor
@@ -3,7 +3,7 @@
 USING: accessors combinators kernel math sequences strings sets
 assocs prettyprint.backend prettyprint.custom make lexer
 namespaces parser arrays fry locals regexp.minimize
-regexp.parser regexp.nfa regexp.dfa
+regexp.parser regexp.nfa regexp.dfa regexp.classes
 regexp.transition-tables splitting sorting regexp.ast
 regexp.negation regexp.matchers regexp.compiler ;
 IN: regexp
@@ -27,6 +27,7 @@ TUPLE: regexp
 
 TUPLE: reverse-matcher regexp ;
 C: <reverse-matcher> reverse-matcher
+! Reverse matchers won't work properly with most combinators, for now
 
 <PRIVATE
 
@@ -39,21 +40,31 @@ C: <reverse-matcher> reverse-matcher
 : <reversed-option> ( ast -- reversed )
     "r" string>options <with-options> ;
 
+M: lookahead question>quot ! Returns ( index string -- ? )
+    term>> ast>dfa dfa>shortest-quotation ;
+
+M: lookbehind question>quot ! Returns ( index string -- ? )
+    term>> <reversed-option>
+    ast>dfa dfa>reverse-shortest-quotation
+    [ [ 1- ] dip ] prepose ;
+
 : compile-reverse ( regexp -- regexp )
     dup '[
         [
             _ get-ast <reversed-option>
-            ast>dfa dfa>quotation
+            ast>dfa dfa>reverse-quotation
         ] unless*
     ] change-reverse-dfa ;
 
-M: regexp match-index-from ( string regexp -- index/f )
+M: regexp match-index-from
     compile-regexp dfa>> <quot-matcher> match-index-from ;
 
-M: reverse-matcher match-index-from ( string regexp -- index/f )
-    [ <reversed> ] [ regexp>> compile-reverse reverse-dfa>> ] bi*
+M: reverse-matcher match-index-from
+    regexp>> compile-reverse reverse-dfa>>
     <quot-matcher> match-index-from ;
 
+! The following two should do some caching
+
 : find-regexp-syntax ( string -- prefix suffix )
     {
         { "R/ "  "/"  }
diff --git a/basis/regexp/transition-tables/transition-tables.factor b/basis/regexp/transition-tables/transition-tables.factor
index 2fad7451b0..89471d2ce2 100644
--- a/basis/regexp/transition-tables/transition-tables.factor
+++ b/basis/regexp/transition-tables/transition-tables.factor
@@ -1,7 +1,7 @@
 ! Copyright (C) 2008 Doug Coleman.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors arrays assocs fry hashtables kernel sequences
-vectors locals ;
+vectors locals regexp.classes ;
 IN: regexp.transition-tables
 
 TUPLE: transition-table transitions start-state final-states ;
@@ -12,10 +12,11 @@ TUPLE: transition-table transitions start-state final-states ;
         H{ } clone >>final-states ;
 
 : maybe-initialize-key ( key hashtable -- )
+    ! Why do we have to do this?
     2dup key? [ 2drop ] [ [ H{ } clone ] 2dip set-at ] if ;
 
 :: (set-transition) ( from to obj hash -- )
-    to hash maybe-initialize-key
+    to condition? [ to hash maybe-initialize-key ] unless
     from hash at
     [ [ to obj ] dip set-at ]
     [ to obj associate from hash set-at ] if* ;
@@ -31,3 +32,23 @@ TUPLE: transition-table transitions start-state final-states ;
 
 : add-transition ( from to obj transition-table -- )
     transitions>> (add-transition) ;
+
+: map-set ( assoc quot -- new-assoc )
+    '[ drop @ dup ] assoc-map ; inline
+
+: rewrite-transitions ( transition-table assoc quot -- transition-table )
+    [
+        [ clone ] dip
+        [ '[ _ condition-at ] change-start-state ]
+        [ '[ [ _ at ] map-set ] change-final-states ]
+        [ ] tri
+    ] dip '[ _ @ ] change-transitions ; inline
+
+: number-transitions ( transitions numbering -- new-transitions )
+    dup '[
+        [ _ at ]
+        [ [ _ condition-at ] assoc-map ] bi*
+    ] assoc-map ;
+
+: transitions-at ( transitions numbering -- transitions )
+    [ number-transitions ] rewrite-transitions ;