Loading DB routines from perl5db.pl version 1.19
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main::(-e:1):   1
  DB<1> $Foo::VERSION = 1;

  DB<2> sub Foo::new { bless {}, shift }

  DB<3> x UNIVERSAL::isa( 'Foo', 'UNIVERSAL' );
0  1
  DB<4> x UNIVERSAL::isa( 'Foo', 'UNIVERSAL' );
0  1
  DB<5> x UNIVERSAL::isa( 'Foo', 'UNIVERSAL' );
0  1
  DB<6> @Foo::ISA = ();

  DB<7> x UNIVERSAL::isa( 'Foo', 'UNIVERSAL' );
0  1
  DB<8> x UNIVERSAL::isa( 'Foo', 'UNIVERSAL' );
0  ''
  DB<9> x UNIVERSAL::isa( 'Foo', 'UNIVERSAL' );
0  ''
  DB<10>