! This word takes three string from the stack, finds all occurences
! of "math" in "string" and replaces them with "replace"

: replace-string ( string match replace -- string' )
    '[ [ _ ?head [ _ % ] [ [ first , ] [ rest ] bi ] if
        dup empty? not ] loop ] "" make swap drop ;

! For instance
"cheesecake" "cake" "pie" replace-string
! Leaves "cheesepie" on the stack