I might do something like this:

use strict;
use warnings;

open my $infile, '<', 'sss.txt' or die $!;

while( my $line = <$infile> ) {
    $line =~ /^$/ and die "Blank line detected at $.\n";
    $line =~ /^#/ and next;
    print "$.: $line";
}

close $infile;
[download]

The first regexp matches (thus triggering the die) if the line is empty, or empty with a newline character at the end.

The second regexp matches (thus skipping to the next line) if a '#' is found as the first character of the line.