How about this: 

( defined($p) ? '1' . $p  : 0 ) eq ( defined($q) ? '1' . $q  : 0 )

[download]

For example:

use strict;
use warnings;

my %strings = (
    'undef' => undef,
    'empty' => '',
    'string' => '0'
);

my @pairs = (
    [ 'undef' , 'undef'  ],
    [ 'undef' , 'empty'  ],
    [ 'undef' , 'string' ],
    [ 'empty' , 'empty'  ],
    [ 'empty' , 'string' ],
    [ 'string', 'string' ],
);

for ( @pairs ) {
    my ($p,$q) = @strings{@$_};
    my $cmp = ( (defined($p) ? '1' . $p  : 0) 
                eq
                (defined($q) ? '1' . $q  : 0)    
              ) ? 'true' : 'false';
    print join(" eq ", @$_), " = $cmp\n";
}

[download]

Result:

undef eq undef = true
undef eq empty = false
undef eq string = false
empty eq empty = true
empty eq string = false
string eq string = true

[download]

-xdg

Code written by xdg and posted on PerlMonks is public domain. It is provided as is with no warranties, express or implied, of any kind. Posted code may not have been tested. Use of posted code is at your own risk.

In reply to Re: Comparing undefined values by xdg
in thread Comparing undefined values by Ovid

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