diff --git a/src/Phsyche.package/PEnv.class/instance/lookupAt.put..st b/src/Phsyche.package/PEnv.class/instance/lookupAt.put..st
new file mode 100644
index 0000000..ac8782b
--- /dev/null
+++ b/src/Phsyche.package/PEnv.class/instance/lookupAt.put..st
@@ -0,0 +1,9 @@
+dictionary access
+lookupAt: key put: val
+	| found |
+	found := self at: key ifAbsent: nil.
+	found
+		ifNil: [ parent
+				ifNotNil: [ :arg | parent lookupAt: key put: val ]
+				ifNil: [ KeyNotFound signal: key , ' not found in the environment' ] ]
+		ifNotNil: [ :arg | self at: key put: val ]
\ No newline at end of file
diff --git a/src/Phsyche.package/PEnvTest.class/instance/testSetAtRightLevel.st b/src/Phsyche.package/PEnvTest.class/instance/testSetAtRightLevel.st
new file mode 100644
index 0000000..18aba52
--- /dev/null
+++ b/src/Phsyche.package/PEnvTest.class/instance/testSetAtRightLevel.st
@@ -0,0 +1,9 @@
+tests
+testSetAtRightLevel
+	outer at: #dad put: 'donald'.
+	inner at: #son put: 'riri'.
+	self assert: (inner at: #son) = 'riri'.
+	inner lookupAt: #son put: 'fifi'.
+	self assert: (outer at: #dad) = 'donald'.
+	outer lookupAt: #dad put: 'piscou'.
+	self assert: (outer at: #dad) = 'piscou'.
\ No newline at end of file
diff --git a/src/Phsyche.package/PEnvTest.class/instance/testSetLookup.st b/src/Phsyche.package/PEnvTest.class/instance/testSetLookup.st
new file mode 100644
index 0000000..f6750d1
--- /dev/null
+++ b/src/Phsyche.package/PEnvTest.class/instance/testSetLookup.st
@@ -0,0 +1,9 @@
+tests
+testSetLookup
+	outer at: #dad put: 'donald'.
+	inner at: #son put: 'riri'.
+	self assert: (inner at: #dad) = 'donald'.
+	inner lookupAt: #dad put: 'picsou'.
+	self assert: (outer at: #dad) = 'picsou'.
+	self assert: (inner at: #dad) = 'picsou'.
+	self deny: (inner keys includes: #dad)
\ No newline at end of file
diff --git a/src/Phsyche.package/PProc.class/instance/env..st b/src/Phsyche.package/PProc.class/instance/env..st
new file mode 100644
index 0000000..e0f1181
--- /dev/null
+++ b/src/Phsyche.package/PProc.class/instance/env..st
@@ -0,0 +1,3 @@
+accessing
+env: e
+	env := e
\ No newline at end of file
diff --git a/src/Phsyche.package/PProc.class/instance/env.st b/src/Phsyche.package/PProc.class/instance/env.st
new file mode 100644
index 0000000..cf85606
--- /dev/null
+++ b/src/Phsyche.package/PProc.class/instance/env.st
@@ -0,0 +1,3 @@
+accessing
+env
+ ^ env
\ No newline at end of file
diff --git a/src/Phsyche.package/PProc.class/properties.json b/src/Phsyche.package/PProc.class/properties.json
index 57582f2..738b8f1 100644
--- a/src/Phsyche.package/PProc.class/properties.json
+++ b/src/Phsyche.package/PProc.class/properties.json
@@ -7,7 +7,8 @@
 	"commentStamp" : "<historical>",
 	"instvars" : [
 		"params",
-		"body" ],
+		"body",
+		"env" ],
 	"name" : "PProc",
 	"pools" : [
 		 ],
diff --git a/src/Phsyche.package/Phsyche.class/instance/divBinding.st b/src/Phsyche.package/Phsyche.class/instance/divBinding.st
index 4bcc678..cc58235 100644
--- a/src/Phsyche.package/Phsyche.class/instance/divBinding.st
+++ b/src/Phsyche.package/Phsyche.class/instance/divBinding.st
@@ -1,3 +1,3 @@
 as yet unclassified
 divBinding
-	^ #+ -> [ :e :v | e / v asFloat ]
\ No newline at end of file
+	^ #/ -> [ :e :v | e / v asFloat ]
\ No newline at end of file
diff --git a/src/Phsyche.package/Phsyche.class/instance/eval.in..st b/src/Phsyche.package/Phsyche.class/instance/eval.in..st
index fbfa18a..b1d0b64 100644
--- a/src/Phsyche.package/Phsyche.class/instance/eval.in..st
+++ b/src/Phsyche.package/Phsyche.class/instance/eval.in..st
@@ -12,6 +12,8 @@ eval: expr in: environ
 						fst = #define ifTrue: [ ^ self evalDefine: expr in: environ ]. "defines the value"
 						fst = #if ifTrue: [ ^ self evalIf: expr in: environ]. "evaluates if"
 						fst = #lambda ifTrue: [ ^ self evalLambda: expr in: environ ]. "evaluates lambda"
+						fst = #begin ifTrue: [ ^ self evalBegin: expr in: environ ]. "evaluates begin"
 						fst = #quote ifTrue: [ ^ expr second ]. "returns the value unevaluated"
-						^ self evalApp: expr in: environ
+						fst = #set ifTrue: [ ^ self evalSet: expr in: environ ]. "evaluates set"
+						^ self evalApp: expr in: environ "everything else is treated as fn application"
 					]
\ No newline at end of file
diff --git a/src/Phsyche.package/Phsyche.class/instance/evalApp.in..st b/src/Phsyche.package/Phsyche.class/instance/evalApp.in..st
index 8da53a8..7c47c39 100644
--- a/src/Phsyche.package/Phsyche.class/instance/evalApp.in..st
+++ b/src/Phsyche.package/Phsyche.class/instance/evalApp.in..st
@@ -3,5 +3,5 @@ evalApp: expr in: environ
 	| proc newEnv |
 	proc := self eval: expr first in: environ.
 	newEnv := proc setParamEnv: (expr allButFirst collect: [ :e | self eval: e in: environ ])
-						in: environ.
+						in: proc env.
 	^ self eval: proc body in: newEnv
\ No newline at end of file
diff --git a/src/Phsyche.package/Phsyche.class/instance/evalBegin.in..st b/src/Phsyche.package/Phsyche.class/instance/evalBegin.in..st
new file mode 100644
index 0000000..706423a
--- /dev/null
+++ b/src/Phsyche.package/Phsyche.class/instance/evalBegin.in..st
@@ -0,0 +1,5 @@
+as yet unclassified
+evalBegin: expr in: environ
+	| res |
+	expr allButFirst do: [ :each | res := self eval: each in: environ ].
+	^ res
\ No newline at end of file
diff --git a/src/Phsyche.package/Phsyche.class/instance/evalLambda.in..st b/src/Phsyche.package/Phsyche.class/instance/evalLambda.in..st
index 6fc30e9..043dfd7 100644
--- a/src/Phsyche.package/Phsyche.class/instance/evalLambda.in..st
+++ b/src/Phsyche.package/Phsyche.class/instance/evalLambda.in..st
@@ -1,3 +1,3 @@
 as yet unclassified
 evalLambda: expr in: environ
-	^ PProc new params: expr second; body: expr third
+	^ PProc new params: expr second; body: expr third; env: environ
diff --git a/src/Phsyche.package/Phsyche.class/instance/evalSet.in..st b/src/Phsyche.package/Phsyche.class/instance/evalSet.in..st
new file mode 100644
index 0000000..059cfc8
--- /dev/null
+++ b/src/Phsyche.package/Phsyche.class/instance/evalSet.in..st
@@ -0,0 +1,4 @@
+as yet unclassified
+evalSet: expr in: environ
+	environ lookupAt: expr second put: (self eval: expr third in: environ).
+	^ #undefined
\ No newline at end of file
diff --git a/src/Phsyche.package/Phsyche.class/instance/initialize.st b/src/Phsyche.package/Phsyche.class/instance/initialize.st
index 87d0528..d5b9a66 100644
--- a/src/Phsyche.package/Phsyche.class/instance/initialize.st
+++ b/src/Phsyche.package/Phsyche.class/instance/initialize.st
@@ -1,6 +1,6 @@
 initialization
 initialize
 	super initialize.
-	env := Dictionary new.
+	env := PEnv new.
 	prims := OrderedCollection new.
 	self initializeEnvBindings
\ No newline at end of file
diff --git a/src/Phsyche.package/Phsyche.class/instance/minusBinding.st b/src/Phsyche.package/Phsyche.class/instance/minusBinding.st
index ac392b3..db12a38 100644
--- a/src/Phsyche.package/Phsyche.class/instance/minusBinding.st
+++ b/src/Phsyche.package/Phsyche.class/instance/minusBinding.st
@@ -1,3 +1,3 @@
 as yet unclassified
 minusBinding
-	^ #+ -> [ :e :v | e - v ]
\ No newline at end of file
+	^ #- -> [ :e :v | e - v ]
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testEvalBegin.st b/src/Phsyche.package/PhsycheTest.class/instance/testEvalBegin.st
new file mode 100644
index 0000000..0176219
--- /dev/null
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testEvalBegin.st
@@ -0,0 +1,3 @@
+tests
+testEvalBegin
+	self assert: (ph parseAndEval: '(begin 1 2 3)') equals: 3
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testEvalBeginSet.st b/src/Phsyche.package/PhsycheTest.class/instance/testEvalBeginSet.st
new file mode 100644
index 0000000..8497623
--- /dev/null
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testEvalBeginSet.st
@@ -0,0 +1,3 @@
+tests
+testEvalBeginSet
+	self assert: (ph parseAndEval: '(begin (define x 1) (set x 2) x)') equals: 2
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testEvalSetAtCorrectLevel.st b/src/Phsyche.package/PhsycheTest.class/instance/testEvalSetAtCorrectLevel.st
new file mode 100644
index 0000000..6f0c000
--- /dev/null
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testEvalSetAtCorrectLevel.st
@@ -0,0 +1,13 @@
+tests
+testEvalSetAtCorrectLevel
+	| proc |
+	ph parseAndEval: '
+		(define fy3
+			((lambda (x)
+				(lambda (y)
+					(begin
+						(set x (+ x 2))
+						(+ x y))))
+			3))'.
+	proc := ph eval: #fy3.
+	self assert: (ph parseAndEval: '(fy3 5)') equals: 10
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testEvalSimpleSet.st b/src/Phsyche.package/PhsycheTest.class/instance/testEvalSimpleSet.st
new file mode 100644
index 0000000..c6eb3be
--- /dev/null
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testEvalSimpleSet.st
@@ -0,0 +1,5 @@
+tests
+testEvalSimpleSet
+	self assert: (ph parseAndEval: '(define x2 21') equals: #undefined.
+	self assert: (ph parseAndEval: '(set x2 22)') equals: #undefined.
+	self assert: (ph parseAndEval: 'x2') equals: 22.
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testLambdaProcedureExecution.st b/src/Phsyche.package/PhsycheTest.class/instance/testLambdaProcedureExecution.st
index 7da50e0..eb4c981 100644
--- a/src/Phsyche.package/PhsycheTest.class/instance/testLambdaProcedureExecution.st
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testLambdaProcedureExecution.st
@@ -1,3 +1,3 @@
-as yet unclassified
+tests
 testLambdaProcedureExecution
 	self assert: (ph parseAndEval: '((lambda (x) (* x x)) 3)') equals: 9.
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testProcedureDefinition.st b/src/Phsyche.package/PhsycheTest.class/instance/testProcedureDefinition.st
index ed52490..263dfd5 100644
--- a/src/Phsyche.package/PhsycheTest.class/instance/testProcedureDefinition.st
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testProcedureDefinition.st
@@ -1,4 +1,4 @@
-as yet unclassified
+tests
 testProcedureDefinition
 	| proc |
 	ph parseAndEval: '(define squared (lambda (x) (* x x)))'.
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testProcedureExecution.st b/src/Phsyche.package/PhsycheTest.class/instance/testProcedureExecution.st
index dd50c94..503c375 100644
--- a/src/Phsyche.package/PhsycheTest.class/instance/testProcedureExecution.st
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testProcedureExecution.st
@@ -1,4 +1,4 @@
-as yet unclassified
+tests
 testProcedureExecution
 	ph parseAndEval: '(define squared (lambda (x) (* x x)))'.
 	self assert: (ph parseAndEval: '(squared 3)') equals: 9
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testSimpleClosure.st b/src/Phsyche.package/PhsycheTest.class/instance/testSimpleClosure.st
new file mode 100644
index 0000000..5d052a6
--- /dev/null
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testSimpleClosure.st
@@ -0,0 +1,10 @@
+tests
+testSimpleClosure
+	| res |
+	res := ph eval: (ph parse: '(
+		((lambda (x)
+			(lambda (y)
+				(+ x y)))
+			3)
+		7)').
+	self assert: res equals: 10
\ No newline at end of file
diff --git a/src/Phsyche.package/PhsycheTest.class/instance/testSimpleClosureIntrospection.st b/src/Phsyche.package/PhsycheTest.class/instance/testSimpleClosureIntrospection.st
new file mode 100644
index 0000000..f49435c
--- /dev/null
+++ b/src/Phsyche.package/PhsycheTest.class/instance/testSimpleClosureIntrospection.st
@@ -0,0 +1,11 @@
+tests
+testSimpleClosureIntrospection
+	| proc |
+	ph parseAndEval: '(define fy3
+		((lambda (x)
+			(lambda (y)
+			x))
+		3))'.
+	proc := ph parseAndEval: '#fy3'.
+	self assert: proc params equals: #(y).
+	self assert: (proc env at: #x) equals: 3.
\ No newline at end of file