to be prepared for the general case, where the columns have names...

Still makes no sense to waste cycles sorting hash keys:

#! perl -slw
use strict;

my @colnames = split ' ', <DATA>;
my @totals;
while( <DATA> ) {
    my @cols = split;
    $totals[ $_ ] += $cols[ $_ ] for 0 .. $#cols;
}

printf "%10s:%u\n", $colnames[$_], $totals[$_] for 0 .. $#totals;

__DATA__
alpha    beta    gamma    delta
1    2    3    4
5    6    7    8
9    10    11    12
[download]

Produces:

C:\test>junk
     alpha:15
      beta:18
     gamma:21
     delta:24
[download]