I don't see the need for this.

use Text::ParseWords;
$str = "a       b               c";
@f = split /\t/, $str;
print scalar @f, "\n";
@f = parse_line('\t', 0, $str);
print scalar @f, "\n";
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output:

[root@localhost root]# perl temp.pl
4
4
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Both parse_line and split handle the null field.