s/iter   original late_chomp  rand_seek
original       4.83         --        -9%      -100%
late_chomp     4.39        10%         --      -100%
rand_seek  1.20e-03    402667%    365992%         --

##</code><code>##

# assumes a global "$n" and "$file"
sub rand_seek {
    my $size = $n || 3; # sample size
    my (@sample, @seen, $line, $pos_after);
    my $filesize = -s $file;
    open(my $fh, $file) or die;
    while (@sample < $size) {
        seek($fh,int(rand($filesize)),0);
        <$fh>; # skip this fragment of a line
        $line = <$fh>; # get the next line
        $pos_after = tell($fh);
        next if grep { $pos_after == $_ } @seen;
        chomp $line;
        push @sample, $line if $line;
        push @seen, $pos_after;
    }
    close $fh
}