Part I
The while loop looks better like this:

open (INFILE, "input_file.csv") || die "Cannot open file!";
<INFILE>;
while (<INFILE>)
{
    $ix++;

    $sec = [ split(/\;/, $_) ];
    next unless (scalar(@$sec))
    
    if (length($sec->[9]) > 12)
    {
        $memid = lc(substr $sec->[9], 4, 8);
    } else {
        $memid = $sec->[9] eq '' ? 'FORCEMEMID' : $sec->[9];
    }
    $list{$memid}{$ix} = $sec;
}
[download]

If $memid don't have the data in the last index of @$sec you don't need the chomp and the chop.
Where is declared %dbsrv?
End of Part I