From @cpansprout

This little script (part of a test I’m preparing for part of bug #75176)—

use warnings;
{
@​Pet​::ISA = "Tike";
@​Tike​::ISA = "Barker";

sub Barker​::speak { "Woof!" }
sub Latrator​::speak { "Bow-wow!" }

my $pet = bless [], "Pet";

@​Dog​::ISA = 'Latrator';
my $tike_glob = delete $​::{'Tike​::'};
$​::{'Tike​::'} = delete $​::{'Dog​::'};

$pet->speak;

undef $tike_glob;
$pet->speak;
}

—produces these warnings, as of perl 5.10.0​:

Can't locate package Dog for @​Pet​::ISA at - line 18.
Can't locate package Dog for @​Pet​::ISA at - line 3.
Can't locate package Dog for @​Pet​::ISA at - line 3.
Can't locate package Dog for @​Pet​::ISA at - line 3.

Flags​:
  category=core
  severity=low

Site configuration information for perl 5.13.3​:

Configured by sprout at Thu Aug 12 17​:53​:37 PDT 2010.

Summary of my perl5 (revision 5 version 13 subversion 3 patch v5.13.3-193-g798ae1b) configuration​:
  Snapshot of​: 798ae1b
  Platform​:
  osname=darwin, osvers=10.4.0, archname=darwin-2level
  uname='darwin pint.local 10.4.0 darwin kernel version 10.4.0​: fri apr 23 18​:28​:53 pdt 2010; root​:xnu-1504.7.4~1release_i386 i386 '
  config_args='-de -Dusedevel'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=undef, usemultiplicity=undef
  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
  use64bitint=undef, use64bitall=undef, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='cc', ccflags ='-fno-common -DPERL_DARWIN -no-cpp-precomp -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
  optimize='-O3',
  cppflags='-no-cpp-precomp -fno-common -DPERL_DARWIN -no-cpp-precomp -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
  ccversion='', gccversion='4.2.1 (Apple Inc. build 5664)', gccosandvers=''
  intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
  ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
  alignbytes=8, prototype=define
  Linker and Libraries​:
  ld='env MACOSX_DEPLOYMENT_TARGET=10.3 cc', ldflags =' -fstack-protector -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib
  libs=-ldbm -ldl -lm -lutil -lc
  perllibs=-ldl -lm -lutil -lc
  libc=/usr/lib/libc.dylib, so=dylib, useshrplib=false, libperl=libperl.a
  gnulibc_version=''
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=bundle, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags=' -bundle -undefined dynamic_lookup -L/usr/local/lib -fstack-protector'

Locally applied patches​:
 

@​INC for perl 5.13.3​:
  /usr/local/lib/perl5/site_perl/5.13.3/darwin-2level
  /usr/local/lib/perl5/site_perl/5.13.3
  /usr/local/lib/perl5/5.13.3/darwin-2level
  /usr/local/lib/perl5/5.13.3
  /usr/local/lib/perl5/site_perl
  .

Environment for perl 5.13.3​:
  DYLD_LIBRARY_PATH (unset)
  HOME=/Users/sprout
  LANG=en_US.UTF-8
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)
  PATH=/usr/bin​:/bin​:/usr/sbin​:/sbin​:/usr/local/bin​:/usr/X11/bin​:/usr/local/bin
  PERL_BADLANG (unset)
  SHELL=/bin/bash

From @cpansprout

On Aug 22, 2010, at 12​:18 PM, Father Chrysostomos wrote​:

This little script (part of a test I’m preparing for part of bug #75176)—

use warnings;
{
@​Pet​::ISA = "Tike";
@​Tike​::ISA = "Barker";

sub Barker​::speak { "Woof!" }
sub Latrator​::speak { "Bow-wow!" }

my $pet = bless [], "Pet";

@​Dog​::ISA = 'Latrator';
my $tike_glob = delete $​::{'Tike​::'};
$​::{'Tike​::'} = delete $​::{'Dog​::'};

$pet->speak;

undef $tike_glob;
$pet->speak;
}

—produces these warnings, as of perl 5.10.0​:

Can't locate package Dog for @​Pet​::ISA at - line 18.
Can't locate package Dog for @​Pet​::ISA at - line 3.
Can't locate package Dog for @​Pet​::ISA at - line 3.
Can't locate package Dog for @​Pet​::ISA at - line 3.

It’s worse. A slight tweak to the script shows that the warnings are not erroneous, but show a real bug​: When Tike is aliased to Dog, Dog’s methods are ignored, but not those of its superclass.

use warnings;
{
@​Pet​::ISA = "Tike";
@​Tike​::ISA = "Barker";

sub Barker​::speak { warn "Woof!" }
sub Latrator​::speak { warn "Bow-wow!" }

my $pet = bless [], "Pet";

$pet->speak;

sub Dog​::speak { warn "Hello" }
@​Dog​::ISA = 'Latrator';
*Tike​:: = delete $​::{'Dog​::'};

$pet->speak;
}

From @cpansprout

On Sun Oct 24 21​:59​:55 2010, some naughty individual wrote​:

It’s worse. A slight tweak to the script shows that the warnings are
not erroneous, but show a real bug​: When Tike is aliased to Dog, Dog’s
methods are ignored, but not those of its superclass.

use warnings;
{
@​Pet​::ISA = "Tike";
@​Tike​::ISA = "Barker";

sub Barker​::speak { warn "Woof!" }
sub Latrator​::speak { warn "Bow-wow!" }

my $pet = bless [], "Pet";

$pet->speak;

sub Dog​::speak { warn "Hello" }
@​Dog​::ISA = 'Latrator';
*Tike​:: = delete $​::{'Dog​::'};

$pet->speak;
}

Fixed by 8b9e80a.

@cpansprout - Status changed from 'new' to 'resolved'