Hi choroba,

Maybe the key doesn't exist in the hash at all?

The defined check would still catch that and there wouldn't be a warning. And if $cell was undef, the warning would be "Use of uninitialized value $cell in hash element", not "Use of uninitialized value $data in string eq" as the OP posted here.

use warnings;
use strict;

my $sheet = {
    'X92' => '',
    'AA571' => '0.00',
    'AA842' => '0.00',
    'B6' => '0',
    'E47' => 'SRAM (ssbw)',
    'M83' => '',
    'X55' => undef,
    'B29' => '0' };

sub test {
    my $cell = shift;
    if(defined $sheet->{$cell} && length($sheet->{$cell}))
        { print "Yes\n" }
    else { print "No\n" }
}

test(undef);
test('A12');
test('X55');
test('M83');
test('B29');
test('E47');

__END__

Use of uninitialized value $cell in hash element at ...
No
No
No
No
Yes
Yes
[download]

Regards,
-- Hauke D