I hate the software that does not keep the return value consistent. Short of asking a parser for an array reference (somehow) regardless of number of items present, however, I do not see a parser to always return an array reference in the situation described. With that out of the way ...

Your problem seems to be of variable scope. Why do you have "my" in ...

if (exists($data->{channel}->{title})) {
  ...
  my $data->{channel}->{item}->[0]=$mydata;
  ...
}
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...? After the end of the if-block, $data->{channel}->{item}->[0] ceases to exist due to my operator.

use strict; use warnings; use Data::Dumper;

my $x;
{
   my $x->{a}->[0] = "no you don't!";
   #  my op also affects unrelated keys. Why?
      $x->{c}->[0] = "try this with previous 'my' for extra fun";
}
{
   $x->{b}->[0] = "now you see";
}
print Dumper $x;

__END__
$VAR1 = {
          'b' => [
                   'now you see'
                 ]
        };
[download]

After tobyink & haukex had set me straight, please ignore the above code; try this ...

use strict; use warnings; use Data::Dumper;

my $x;
{
   my $x->{a}->[0] = "no you don't!";
}
{
   $x->{b}->[0] = "now you see";
}
print Dumper $x;

__END__
$VAR1 = {
          'b' => [
                   'now you see'
                 ]
        };
[download]