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

In reply to Re: Re: Re: exists() unexpected behavior by knobunc
in thread exists() unexpected behavior by Richard

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