Re: Why are these undefs different?

[BillKSmith]

A little more code handles all the common errors correctly without throwing an exception and without altering the original data.

use strict;
use warnings;
use List::Util qw(first);
use Scalar::Util qw(looks_like_number);
use Test::More tests=>5;

sub first_a_value {
    my @x = @_;
    my $refer = first {
        exists $_->{aaa}
        and looks_like_number($_->{aaa})
        and $_->{aaa} < 4 
    } @x;
    my $value = undef;
    $value = $refer->{aaa} if defined $refer;
    return $value;
}

my @x;
my $aaa;


@x = ( {aaa=>3} );
$aaa = first_a_value(@x);
ok ($aaa == 3, 'valid value');

@x = ( {aaa=>100} );
$aaa = first_a_value(@x);
ok (!defined($aaa), 'no numer small enough');

@x = ( {aaa=>'foo'} );
$aaa = first_a_value(@x);
ok (!defined($aaa), 'not a number');

@x = ( {bbb=>3} );
$aaa = first_a_value(@x);
ok (!defined($aaa), 'no aaa');


@x = ( {} );
$aaa = first_a_value(@x);
ok (!defined($aaa), 'no hash');

UPDATD - Added tests accidentally omitted.