Try also this variations:

#!/usr/bin/env perl

use strict;
use warnings;
use feature qw(say);
use Path::Tiny;

my $file = $ARGV[0];

while (<>) {
    chomp;
    say length;
}

say q(--);

open my $fh, q(<), $file or die $!;

while (<$fh>) {
    chomp;
    say length;
}

close $fh;

say q(--);

say length for path($file)->lines( { chomp => 1 } );

__END__

karls-mac-mini:monks karl$ ./lenght.pl file.txt 
6
8
8
3
8
9
--
6
8
8
3
8
9
--
6
8
8
3
8
9
[download]

Best regards, Karl