split does use a regex, as the second parameter passed to it. That being said, perhaps a regex with a capture will effectively propagate an array for you, sans the 'extra characters:'

use Modern::Perl;
use Data::Dumper;

my $a = 'a,b,c,d,,,,,,,';

my @col = $a =~ /([^,]+)/gi;

say Dumper \@col;
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Output:

$VAR1 = [
          'a',
          'b',
          'c',
          'd'
        ];
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However, if you know the number of columns and want to limit split to those, you can do the following:

use Modern::Perl;
use Data::Dumper;

my $a = 'a,b,c,d,,,,,,,';

my @col = ( split ',', $a, )[ 0 .. 3 ];

say Dumper \@col;
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Output:

$VAR1 = [
          'a',
          'b',
          'c',
          'd'
        ];
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Hope this helps!

Update: my @col = split /,+/, $a; produces the same output as both examples above.