Some people smell homework... Me ive got a cold so I cant smell anything....

use strict;
use warnings;
my @list=map{chomp;$_}<DATA>;
my @output;
foreach my $line (@list) {
  foreach my $ofs (0..length($line)-1) {
    $output[$ofs].=substr($line,$ofs,1);
  }
}
print join ("\n",@output),"\n";
__DATA__
ABC
DEF
GHI
JKL
MNO
PQR
STU
[download]

Outputs

ADGJMPS
BEHKNQT
CFILORU

I hope I get a good mark ;-)

Yves / DeMerphq
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Writing a good benchmark isnt as easy as it might look.