use strict;
use warnings;

# use Data::Dumper;  # for debugging

# change this to change what a "number" is.
my $rx_number = qr{ \d+ }xms;

# these variables are intentionally left undefined.
my $largest_n;
my $line_with_largest_n;

LINE:
while (my $line = <STDIN>) {

# print Dumper $line;  # for debug

  # extract all number groups from line.
  my @numbers = $line =~ m{ $rx_number }xmsg;
# print Dumper \@numbers;  # for debug

  # nothing to do unless some numbers were extracted.
  next LINE unless @numbers;

  # extracted some numbers from this line.  find largest.
  my $largest_n_in_line = (sort { $a <=> $b } @numbers)[-1];
# print Dumper $largest_n_in_line;  # for debug

  # nothing to do unless
  #  NO largest n has been seen so far
  #  OR largest n in line is greater than largest n seen so far.
  next LINE unless !defined($largest_n) 
                or $largest_n_in_line > $largest_n
                 ;

  # update largest n and line with largest n.
  $largest_n = $largest_n_in_line;
  $line_with_largest_n = $line;

# print Dumper $largest_n, $line_with_largest_n;  # for debug

  }  # end while LINE

if (defined $line_with_largest_n) {
  print "F$line_with_largest_n";
  }
else {
  print "no line with a number was seen \n";
  }

##</code><code>##

c:\@Work\Perl\monks\SSSufe>perl line_with_lagest_n_1.pl < lines.dat
F1 this year is 2019 1