"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
print "Free chars:\n\t";
for (my $i = 0; $i < length $opt_chars; ++$i, ++$cols) {
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
print "Free chars:\n\t";
for (my $i = 0; $i < length $opt_chars; ++$i, ++$cols) {