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