use strict;
use warnings;

open my $fh1, '>', 'item1.dat' or die "can not open file item1.dat: $!";
open my $fh2, '>', 'item2.dat' or die "can not open file item2.dat: $!";
open my $fh3, '>', 'item3.dat' or die "can not open file item3.dat: $!";
while (<DATA>) {
    next if (/^item/);  # ignore header    
    my @items = split;
    print $fh1 "@items[0..1]\n";
    print $fh2 "@items[2..3]\n";
    print $fh3 "@items[4..5]\n";
}

__DATA__
item1 item2 item3  
0  0    1  S    0  0   
0  0    2  K    0  0   
0  0   23  T    1  M
12 T   24  N    2  L 
45 0   36  V   14  I 
46 0   38  W   16  R 
51 S   39  A   17  L
52 A   42  N   20  E
53 0   43  L   21  G