use Modern::Perl;
use List::MoreUtils qw/pairwise/;
use autodie;

open my $in1, './file1.dat';
open my $in2, './file2.dat';

while (my $first = <$in1> and my $second = <$in2>) {
    my @first  = split / /, $first;
    my @second = split / /, $second;
    my @result = pairwise {$a - $b} @first, @second;
    say "@result";
}