See the other replies for why Perl does this. I have a subroutine I use when I want to get a value from a nested structure only if it exists. You can modify this to do the existence check only if you need that.

use Carp;

sub safe_get {
    my $handle = shift;
    my $ptr = $handle;

    for (my $i = 0; $i < @_; $i++) {
        my $key = $_[$i];

        # Handle each type
        my $type = ref $ptr;
        if (not defined $type) {
            croak "Not a reference.\n";
        }
        elsif ($type eq 'HASH') {
            return undef unless exists $ptr->{$key};
            $ptr = $ptr->{$key};
        }
        elsif ($type eq 'ARRAY') {
            croak "Non numeric array index '$key'."
                unless $key =~ m/^\+?\d+$/;
            croak "Bad array thing '$key'." unless $key >= 0;
            return undef unless $key < @$ptr;

            $ptr = $ptr->[$key];
        }
        else {
            croak "Unable to handle type '$type'";
        }

        # Is this the end?
        return $ptr if $i == @_ - 1;
    }
}

# Usage
my %foo = {bar => [1, {baz => 'xyzzy'}] };

my $value1 = safe_get(\%foo, 'bar', 1, 'baz');
my $value2 = safe_get(\%foo, 'bar', 2, 'baz');

# $value1 is 'xyzzy', $value2 is undef
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-ben

For now, the known workaround is to step carefully down the tree, calling exists at each level before proceeding to the next. In practice, I've not been bitten by this, but maybe it's because I had been bitten once or twice while practicing with references. {grin}

-- Randal L. Schwartz, Perl hacker