You are not clear what you want, nor what your problems are, but to me it looks like you're checking whether the file starts with a 0, and then from character 10 onwards, whether it contains numbers and tabs, with no more than 20 numbers in a row, and no more than 2 tabs in a row either. Can't you just do something like:

if ($line =~ /^0/) {
    my $end = substr ($line, 10);
    unless ($end =~ /[^0-9\t]/ || 
            $end =~ /\t\t/     || 
            $end =~ /[0-9]{21}/) {
        ....
    }
}
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