P:\test>type test.dat
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5
1 2 3 4 5

P:\test>type flip.pl
#! perl -slw
use strict;
my @cols;

push @cols, [ split ] while $_ = <>;

for my $n ( 0 .. $#{ $cols[ 0 ] } ) { 
    print join ' ', map{ $_->[ $n ] } @cols; 
}

P:\test>perl -le "
    open F, qq[ flip test.dat |]; 
    print join '|', split while $_ = <F>; 
"

1|1|1|1|1|1|1|1
2|2|2|2|2|2|2|2
3|3|3|3|3|3|3|3
4|4|4|4|4|4|4|4
5|5|5|5|5|5|5|5