Re: Unexpected behaviour of a tied array (Bug in ActiveState Perl?)

At first I thought it was due to the ALIASING magic that a foreach(@array) does, but it turns out, it has nothing to do with aliasing.

It has to do with string interpolation. If you interpolate our magical $_ in a string, and there is nothing before the "$_", then two FETCHs are performed.

I'm glad this is fixed after 5.6 (works fine in 5.7)

#!/usr/bin/perl

use strict;
use warnings;

package Dummy;

sub TIEARRAY
{
    my $class = shift;
    return bless [], $class;
}

sub STORE
{
    my $self = shift;
    my $index = shift;
    my $value = shift;

    return ($self->[ $index ] = $value );
}

sub FETCH
{
    my $self = shift;
    my $index = shift;

    print STDERR "Now I'm fetching the element with index: $index\n";
    return $self->[ $index ];
}

sub FETCHSIZE
{
    my $self = shift;

    return scalar( @$self );
}

package main;

$|=1;

my @array;
tie @array, 'Dummy';

$array[0] = 'Perl';
$array[1] = 'Monks';

print "for     $_\n" for @array;

print "\n\n fine ", 'x' x 60, "\n\n";

print "foreach $_\n" foreach @array;

print "\n\n fine ", 'x' x 60, "\n\n";

for my $z(@array){
    print "for my  $z\n";
}

print "\n\n fine ", 'x' x 60, "\n\n";

for my $z(@array){
    print "??????\n";
    print $z;
    print "\n";
}


print "\n\n buggy ", 'x' x 60, "\n\n";

{
    local $\="\n";
    print "$_\ta" for @array;
}

print "\n\n fine ", 'x' x 60, "\n\n";

for(@array) {
    my $a = $_;
    print "$a\n";
}

print "\n\n buggy ", 'x' x 60, "\n\n";

for(@array) {
    warn "$_\n";
}

print "\n\noriginal\n\n";

foreach ( @array ) {
    print "$_\n";
    # print $_; print "\n";
}

__END__

E:\dev\LOOSE>perl tie.bug.t
Now I'm fetching the element with index: 0
for     Perl
Now I'm fetching the element with index: 1
for     Monks


 fine xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Now I'm fetching the element with index: 0
foreach Perl
Now I'm fetching the element with index: 1
foreach Monks


 fine xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Now I'm fetching the element with index: 0
for my  Perl
Now I'm fetching the element with index: 1
for my  Monks


 fine xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

??????
Now I'm fetching the element with index: 0
Perl
??????
Now I'm fetching the element with index: 1
Monks


 buggy xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Now I'm fetching the element with index: 0

Now I'm fetching the element with index: 0

Perl    a
Now I'm fetching the element with index: 1

Now I'm fetching the element with index: 1

Monks   a


 fine xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Now I'm fetching the element with index: 0
Perl
Now I'm fetching the element with index: 1
Monks


 buggy xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Now I'm fetching the element with index: 0
Now I'm fetching the element with index: 0
Perl
Now I'm fetching the element with index: 1
Now I'm fetching the element with index: 1
Monks


original

Now I'm fetching the element with index: 0
Now I'm fetching the element with index: 0
Perl
Now I'm fetching the element with index: 1
Now I'm fetching the element with index: 1
Monks

E:\dev\LOOSE>
[download]

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