#!/usr/local/bin/perl -w
use strict;
my  @data;
my $file='data_file';

open( DATA , $file);
@data=<DATA>; ### already read all of $file into @data
close(DATA);
print @data;

while (<$data>) { ### can make this 'for ( @data ) {'
my @fields = split ' ';
for my $row (0..$#fields) {
       push @{$data[$row]}, $fields[$row];
    }
}
use Data::Dumper;
print Dumper \@data;