diff --git a/src/passes/1-parser/pascaligo/.Parser.mly.tag b/src/passes/1-parser/pascaligo/.Parser.mly.tag
index 100f7bb69..ab6790b0f 100644
--- a/src/passes/1-parser/pascaligo/.Parser.mly.tag
+++ b/src/passes/1-parser/pascaligo/.Parser.mly.tag
@@ -1 +1 @@
---explain --external-tokens LexToken --base Parser ParToken.mly
+--table --explain --external-tokens LexToken --base Parser ParToken.mly
diff --git a/src/passes/1-parser/pascaligo/.unlexer.tag b/src/passes/1-parser/pascaligo/.unlexer.tag
new file mode 100644
index 000000000..e69de29bb
diff --git a/src/passes/1-parser/pascaligo/unlexer.ml b/src/passes/1-parser/pascaligo/unlexer.ml
new file mode 100644
index 000000000..0ee7da436
--- /dev/null
+++ b/src/passes/1-parser/pascaligo/unlexer.ml
@@ -0,0 +1,121 @@
+(** Converting the textual representation of tokens produced by Menhir
+    into concrete syntax *)
+
+(* See [ParToken.mly] *)
+
+let gen_sym prefix =
+  let count = ref 0 in
+  fun () -> incr count;
+         prefix ^ string_of_int !count
+
+let id_sym   = gen_sym "id"
+and ctor_sym = gen_sym "C"
+
+let concrete = function
+  (* Keywords *)
+
+  "And"      -> "and"
+| "Begin"    -> "begin"
+| "BigMap"   -> "big_map"
+| "Block"    -> "block"
+| "Case"     -> "case"
+| "Const"    -> "const"
+| "Contains" -> "contains"
+| "Else"     -> "else"
+| "End"      -> "end"
+| "False"    -> "False"
+| "For"      -> "for"
+| "Function" -> "function"
+| "From"     -> "from"
+| "If"       -> "if"
+| "In"       -> "in"
+| "Is"       -> "is"
+| "List"     -> "list"
+| "Map"      -> "map"
+| "Mod"      -> "mod"
+| "Nil"      -> "nil"
+| "Not"      -> "not"
+| "Of"       -> "of"
+| "Or"       -> "or"
+| "Patch"    -> "patch"
+| "Record"   -> "record"
+| "Remove"   -> "remove"
+| "Set"      -> "set"
+| "Skip"     -> "skip"
+| "Then"     -> "then"
+| "To"       -> "to"
+| "True"     -> "True"
+| "Type"     -> "type"
+| "Unit"     -> "Unit"
+| "Var"      -> "var"
+| "While"    -> "while"
+| "With"     -> "with"
+
+  (* Data constructors *)
+
+| "C_None"   -> "None"
+| "C_Some"   -> "Some"
+
+  (* Symbols *)
+
+| "SEMI"     -> ";"
+| "COMMA"    -> ","
+| "LPAR"     -> "("
+| "RPAR"     -> ")"
+| "LBRACE"   -> "{"
+| "RBRACE"   -> "}"
+| "LBRACKET" -> "["
+| "RBRACKET" -> "]"
+| "CONS"     -> "#"
+| "VBAR"     -> "|"
+| "ARROW"    -> "->"
+| "ASS"      -> ":="
+| "EQ"       -> "="
+| "COLON"    -> ":"
+| "LT"       -> "<"
+| "LE"       -> "<="
+| "GT"       -> ">"
+| "GE"       -> ">="
+| "NE"       -> "=/="
+| "PLUS"     -> "+"
+| "MINUS"    -> "  -"
+| "SLASH"    -> "/"
+| "TIMES"    -> "*"
+| "DOT"      -> "."
+| "WILD"     -> "_"
+| "CAT"      -> "^"
+
+  (* Literals *)
+
+| "String"   -> "\"a string\""
+| "Bytes"    -> "0xAA"
+| "Int"      -> "1"
+| "Nat"      -> "1n"
+| "Mutez"    -> "1mutez"
+| "Ident"    -> id_sym ()
+| "Constr"   -> ctor_sym ()
+
+  (* Virtual tokens *)
+
+| "EOF"      -> ""
+
+  (* For completeness of open sum types *)
+
+| _          -> "<Unknown>"
+
+(* Unlexing a sentence *)
+
+let unlex (sentence: string) : Buffer.t =
+  let tokens  = Str.split (Str.regexp " ") sentence in
+  let lexemes = List.map concrete tokens in
+  let buffer  = Buffer.create 31 in
+  let rec trans = function
+      [] -> ()
+  |  [s] -> Buffer.add_string buffer s
+  | s::l -> Buffer.add_string buffer (s ^ " "); trans l
+  in trans lexemes; buffer
+
+(* Reading one line from the standard input channel and unlex it. *)
+
+let out = unlex (input_line stdin) |> Buffer.contents
+let ()  = Printf.printf "%s\n" out