use strict;
use warnings;
use feature 'say';

my $longest;
my $max_length = 0;

my @lines = <DATA>;

for my $line (@lines) {
    chomp($line);
    my $length = length($line);
    if ( $length > $max_length ) {
        $longest = $line;
        $max_length = $length;
    }
}

say "'$longest' was $max_length chars";

__DATA__
Hello, i'm 18

1 this year is 2019 1

1 2 3 - 4