while (<>) {
    # Added a conditional per merlyn's advice
    /(\S*)\s+(\S*)/ or next;
#   /(\S*)\s+(\S*)/;

    push @a, $1 if length $1;
    push @b, $2 if length $2;
}

print "First column output:\n\n@a\n\n",
      "Second column output:\n\n@b\n\n"