By that point in the code, there are no negatives anyway

Here, I think this is what you want:

for my $aref_acc_num (sort { $a->[0] cmp $b->[0] } values %$acc_num) {
    
    push @$all_dta_acc_num, my $tmp = [];
    
    for my $aref (@$aref_acc_num) {
        
        for my $i (0..1) {
            $tmp->[$i] = $aref->[$i];
        }
        
        for my $i (2..$#$aref) {
            if (!defined($tmp->[$i])) {
              $tmp->[$i] = $aref->[$i];
            } elsif ($tmp->[$i]=~m/^[+-]?\d+$/) { #numeric
              $tmp->[$i] = $aref->[$i] if $aref->[$i] > $tmp->[$i];
            } else {
              $tmp->[$i] = $aref->[$i] if $aref->[$i] gt $tmp->[$i];
            }
        }        
    }
}
[download]

This is very close, see the values for "Zilda Mil", it should display "14.0" but instead its getting the "9.0".

This is very close, see the values for "Zilda Mil", it should display "14.0" but instead its getting the "9.0".

Hmmm, yes, this is because it's using 'gt' rather than '<'. I copied the regex from your program. The best solution (if you're on Perl 5.8 or later) is to use looks_like_number:

use Scalar::Util 'looks_like_number';
for my $aref_acc_num (sort { $a->[0] cmp $b->[0] } values %$acc_num) {
    
    push @$all_dta_acc_num, my $tmp = [];
    
    for my $aref (@$aref_acc_num) {
        
        for my $i (0..1) {
            $tmp->[$i] = $aref->[$i];
        }
        
        for my $i (2..$#$aref) {
            if (!defined($tmp->[$i])) {
              $tmp->[$i] = $aref->[$i];
            } elsif (looks_like_number($tmp->[$i])) {
              $tmp->[$i] = $aref->[$i] if $aref->[$i] > $tmp->[$i];
            } else {
              $tmp->[$i] = $aref->[$i] if $aref->[$i] gt $tmp->[$i];
            }
        }        
    }
}
[download]

If you're on an earlier Perl, see perlfaq4.

          [
            'Auser Ferro',
            '987778999',
            '2008-11-30',
            'W',
            '888',
            '0',
            '0',
            '0',
            '1',
            '2',
            '4',
            '0',
            '-5.00',
            '0',
            '0',
            '0',
            '0',
            '0',
            '0',
            '2.0',
            '2008',
            '1112399'
          ],
[download]