It depends on what you mean by empty.

Your test unless($list eq " ") does not test for an empty string, but for a visible space: is that empty?

Perl uses the scalar value of undef for "empty", although you could consider zero as being empty as well: zero and empty string equate to false.

Not sure why other monks assumed your data was coming from a file, maybe it is but you don't say that. Interestingly, when I downloaded your data I found you had trailing spaces after the first b, c, and d. Maybe that is your problem? Here is my solution, which also removes trailing white-space:

use warnings;
use strict;

my @array;

while (my $list = <DATA>) {

    # Remove trailing white-space, no need for chomp
    $list =~ s/\s+$//;  
    
    # If the data is coming from a file (like this), 
    # then you don't need to test defined
    
    if (defined $list and $list) {
        push(@array, $list);
    }

}

print "@array\n";

__DATA__
a

b 
c 

d 

a
a
c

d
c
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