gv.c AOK

     Can't locate package %s for @%s::ISA
	@ISA = qw(Fred); joe()

     Name "main::a" used only once: possible typo

  Mandatory Warnings ALL TODO
  ------------------

    Had to create %SVf unexpectedly		[gv_fetchpv]
    Attempt to free unreferenced glob pointers	[gp_free]
    
__END__
# gv.c
use warnings 'syntax' ;
@ISA = qw(Fred); joe()
EXPECT
Undefined subroutine &main::joe called at - line 3.
########
# gv.c
no warnings 'syntax' ;
@ISA = qw(Fred); joe()
EXPECT
Undefined subroutine &main::joe called at - line 3.
########
# gv.c
use warnings 'syntax' ;
@ISA = qw(Fred); __PACKAGE__->joe()
EXPECT
While trying to resolve method call main->joe() can not locate package "Fred" yet it is mentioned in @main::ISA (perhaps you forgot to load "Fred"?) at - line 3.
Can't locate object method "joe" via package "main" at - line 3.
########
# gv.c
no warnings 'syntax' ;
@ISA = qw(Fred); __PACKAGE__->joe()
EXPECT
Can't locate object method "joe" via package "main" at - line 3.
########
# gv.c
use warnings 'syntax' ;
{
    package AA;    # this is a deliberate error
#   package A;     # should be this
    sub foo {
       print STDERR "I'm in A's foo\n";
    }
}
{
   package B;
   sub foo {
       print STDERR "I'm in B's foo\n";
   }
}
@C::ISA = qw(A B);
$a = bless [], 'C';
$a->foo();
__END__
EXPECT
While trying to resolve method call C->foo() can not locate package "A" yet it is mentioned in @C::ISA (perhaps you forgot to load "A"?) at - line 18.
I'm in B's foo
########
# gv.c
no warnings 'syntax' ;
{
    package AA;    # this is a deliberate error
#   package A;     # should be this
    sub foo {
       print STDERR "I'm in A's foo\n";
    }
}
{
   package B;
   sub foo {
       print STDERR "I'm in B's foo\n";
   }
}
@C::ISA = qw(A B);
$a = bless [], 'C';
$a->foo();
__END__
EXPECT
I'm in B's foo
########
# gv.c
use warnings 'syntax' ;
{
#   package AA;    # this would be an error
    package A;     # the right thing
    sub foo {
       print STDERR "I'm in A's foo\n";
    }
}
{
   package B;
   sub foo {
       print STDERR "I'm in B's foo\n";
   }
}
@C::ISA = qw(A B);
$a = bless [], 'C';
$a->foo();
__END__
EXPECT
I'm in A's foo
########
# gv.c
$a = ${^ENCODING};
$a = ${^E_NCODING};
${^E_NCODING} = 1; # We pretend this variable never existed.
EXPECT
########
# gv.c
use warnings 'syntax' ;
use utf8;
use open qw( :utf8 :std );
package Ｙ;
@ISA = qw(Fred); joe()
EXPECT
Undefined subroutine &Ｙ::joe called at - line 6.
########
# gv.c
use warnings;
$x = 1;
if ($x) {
    print $y;
}
$a++; # These two should
$b++; # be exempt.
$Foo::a++;
$Foo::b++;
EXPECT
Name "main::y" used only once: possible typo at - line 5.
Use of uninitialized value $y in print at - line 5.
########
# gv.c
use warnings;
$x = 1;
if ($x) {
    $x++;
    print $y;
}
EXPECT
Name "main::y" used only once: possible typo at - line 6.
Use of uninitialized value $y in print at - line 6.
########
# gv.c
use warnings;
$x = 0;
if ($x) {
    print "1\n";
} elsif (!$x) {
    print $y;
} else {
    print "0\n";
}
EXPECT
Name "main::y" used only once: possible typo at - line 7.
Use of uninitialized value $y in print at - line 7.
########
# gv.c
use warnings;
$x = 0;
if ($x) {
    print "1\n";
} elsif (!$x) {
    $x++;
    print $y;
} else {
    print "0\n";
}
EXPECT
Name "main::y" used only once: possible typo at - line 8.
Use of uninitialized value $y in print at - line 8.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
$ㄒ = 1;
if ($ㄒ) {
    print $ʎ;
}
EXPECT
Name "main::ʎ" used only once: possible typo at - line 7.
Use of uninitialized value $ʎ in print at - line 7.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
$ㄒ = 1;
if ($ㄒ) {
    $ㄒ++;
    print $ʎ;
}
EXPECT
Name "main::ʎ" used only once: possible typo at - line 8.
Use of uninitialized value $ʎ in print at - line 8.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
$ㄒ = 0;
if ($ㄒ) {
    print "1\n";
} elsif (!$ㄒ) {
    print $ʎ;
} else {
    print "0\n";
}
EXPECT
Name "main::ʎ" used only once: possible typo at - line 9.
Use of uninitialized value $ʎ in print at - line 9.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
$ㄒ = 0;
if ($ㄒ) {
    print "1\n";
} elsif (!$ㄒ) {
    $ㄒ++;
    print $ʎ;
} else {
    print "0\n";
}
EXPECT
Name "main::ʎ" used only once: possible typo at - line 10.
Use of uninitialized value $ʎ in print at - line 10.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
package 팣칵ぇ;
$ㄒ = 1;
if ($ㄒ) {
    print $ʎ;
}
EXPECT
Name "팣칵ぇ::ʎ" used only once: possible typo at - line 8.
Use of uninitialized value $팣칵ぇ::ʎ in print at - line 8.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
package 팣칵ぇ;
$ㄒ = 1;
if ($ㄒ) {
    $ㄒ++;
    print $ʎ;
}
EXPECT
Name "팣칵ぇ::ʎ" used only once: possible typo at - line 9.
Use of uninitialized value $팣칵ぇ::ʎ in print at - line 9.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
package 팣칵ぇ;
$ㄒ = 0;
if ($ㄒ) {
    print "1\n";
} elsif (!$ㄒ) {
    print $ʎ;
} else {
    print "0\n";
}
EXPECT
Name "팣칵ぇ::ʎ" used only once: possible typo at - line 10.
Use of uninitialized value $팣칵ぇ::ʎ in print at - line 10.
########
# gv.c
use utf8;
use open qw( :utf8 :std );
use warnings;
package 팣칵ぇ;
$ㄒ = 0;
if ($ㄒ) {
    print "1\n";
} elsif (!$ㄒ) {
    $ㄒ++;
    print $ʎ;
} else {
    print "0\n";
}
EXPECT
Name "팣칵ぇ::ʎ" used only once: possible typo at - line 11.
Use of uninitialized value $팣칵ぇ::ʎ in print at - line 11.
########
# https://github.com/Perl/perl5/issues/21271
use v5.36;
no strict;
my $x = $i;
EXPECT
Name "main::i" used only once: possible typo at - line 4.
########
# https://github.com/Perl/perl5/issues/13814
use warnings FATAL => qw(once);
print @Foo::bar, "\n";
print "still alive\n";
EXPECT
OPTION fatal
Name "Foo::bar" used only once: possible typo at - line 3.