| genTree printTree pathList tree |
genTree := [:paths |
    | leaf |
    leaf := paths groupBy: [:path | path first] having: [:g | true].
    leaf associationsDo: [:assoc |
        | newValue |
        newValue := assoc value
            collect: [:val | val allButFirst] thenSelect: [:val | val notEmpty].
        assoc value: (newValue isEmpty
            ifTrue: [newValue]
            ifFalse: [genTree copy fixTemps value: newValue])]].

printTree := [:dic :lev |
    dic keys asSortedCollection do: [:key |
        Transcript crtab: lev; show: key.
        (dic at: key) ifNotEmptyDo: [:child |
            printTree copy fixTemps value: child value: lev + 1]]].

pathList := #('abc\def' 'abc\def\gh' 'abc\def\ij' 'abc\jk\lm' 'de').
pathList := pathList collect: [:each | each subStrings: {$\}].

World findATranscript: nil.
tree := genTree copy fixTemps value: pathList.
printTree copy fixTemps value: tree value: 0

"=>
abc
    def
        gh
        ij
    jk
        lm
de
"