⎕session←{
	(indented main prompt)←⍵
	⎕rawio←'Welcome to APL9',(⎕ucs 10),prompt
	indented←≢prompt

	unindent←{
		⎕rawio←⎕ucs ⍺⍴8
	}
	handleMain←{
		0::⍺
		data←⍵
		⎕rawio←data
		⎕rawio←⎕ucs 10
		⎕rawio←prompt
		≢prompt
	}
	handleError←{
		0::⍺
		(task (error msg taskname))←⍵
		⎕rawio←error,' in [',(⍕task),':',taskname,']'
		_←{⎕rawio←': ', msg} IF msg≢''
		⎕rawio←⎕ucs 10
		⎕rawio←prompt
		≢prompt
	}
	handleQuad←{
		0::⍺
		data←⍵
		⎕rawio←data
		⎕rawio←⎕ucs 10
		⎕rawio←prompt
		≢prompt
	}
	handleQuoteQuad←{
		0::⍺
		data←⍵
		⎕rawio←data
		⍺
	}
	handle←{
		0::⍺
		(task (type data))←⍵
		indented←⍺
		_←indented∘unindent IF (indented>0)∧task≢main
		indented←indented×task≡main
		type≡'→': indented handleMain data
		type≡'!': indented handleError task data
		type≡'⎕': indented handleQuad data 
		type≡'⍞': indented handleQuoteQuad data
		⍵
	}
	{∇ ⍵ handle {1 ⍵}⍇⍬} indented
}&'session'⊢0 ⎕self ('APL9>  ')