#!/usr/bin/perl -w
use strict;

open Spg, '<', 'spg.txt' or die "spg.txt: $!\n";
my @list = split /\s+/, do { local $/; <Spg> };
close Spg;

while (@list){
    # Output 1 and 5...
    print "@list[1,5]\n";
    # ...and throw away the first 7
    splice @list, 0, 7;
}