while (<>) {
  /   ( ^ -? \d+ )  \s+
  # optional minus at start of line, some digits, some space
      (   -? \d+ )
  # same thing, but NOT at start of line
  /x
  # eXplanation mode (m is useless when you read line by line)
  and print;
  # I didn't get the purpose of your print statements -
  # this one will simply print the line if matched.
}