use Devel::Symdump;

  my $x = Mod::idx('some string');
  print "x=$x\n";  # works, x=5

  my $obj = Devel::Symdump->new('Mod'); # crash on 5.10

  package Mod;

  use constant 'STRING' => 'string';

  sub idx {
    my $s = shift;
    return index($s, STRING);
  }

##</code><code>##

  local(*ENTRY) = $val;

##</code><code>##

  if ($symtab && !exists $symtab->{$name}) {
      # No typeglob yet, so we can use a reference as space-
      # efficient proxy for a constant subroutine
      # The check in Perl_ck_rvconst knows that inlinable
      # constants from cv_const_sv are read only. So we have to:
      Internals::SvREADONLY($scalar, 1);
      $symtab->{$name} = \$scalar;
      mro::method_changed_in($pkg);
  } else {
      *$full_name = sub () { $scalar };
  }

##</code><code>##

  index($s, scalar STRING)