Numeric labels not fully supported

[texdraft]

Algol 60 has an unfortunate (and likely unintended) ambiguity around numeric labels:

#lang algol60

begin
  procedure Pop(Q);
    procedure Q;
    begin Q(3); end;
  procedure Pip(A);
    label A;
    begin goto A; end;
  procedure Pap(B);
    integer B;
    begin end;
  Pop(Pap);
  if false then 3:
  else Pop(Pip)
end

should do nothing but instead fails on Pop(Pip). See https://retrocomputing.stackexchange.com/questions/20381/which-extant-algol-60-compilers-fully-support-numeric-labels for some more context.