use strict;
use warnings;
use Data::Dumper;

my @S;
while (<DATA>) {
    push @S, [split];
}
print "-----TRIPLETS-------\n";
print Dumper \@S;

my @new = map { [@{ $_ }[0 .. 1]] } @S;
print Dumper \@new;

__DATA__
b c a
a c d
d e b


##</code><code>##

-----TRIPLETS-------
$VAR1 = [
          [
            'b',
            'c',
            'a'
          ],
          [
            'a',
            'c',
            'd'
          ],
          [
            'd',
            'e',
            'b'
          ]
        ];
$VAR1 = [
          [
            'b',
            'c'
          ],
          [
            'a',
            'c'
          ],
          [
            'd',
            'e'
          ]
        ];