Unless I've misunderstood your re-coding suggestions, they do not produce the OP's desired outcome.

Firstly, I ran that code and got 

hostname1.com
Gateway FAIL
hostname2.com
Gateway FAIL

[download]
which is exactly what I'd expect. The last line was not duplicated. Perhaps you managed to get some whitespace at the end of that line in your input file?

Secondly, you took out both of the newlines you were printing. Since you are now ignoring the blank lines that are in the input (as I said), you still have to create them on the output. You just don't have to remove the newline from the lines that have non-whitespace characters.

So, to be clear, you should have changed the line 

print $line, "\n\n";

[download]
to 
print $line, "\n";

[download]

By the way, these modifications for the blanks are exactly what I was talking about in Re: Delete Duplicate Entry in a text file. To put it together with my code there: 

my $last;
while (my $line = <$fh>) {
    next unless $line =~ /\S/; 
    next if defined $last and $line eq $last;
    print $line, "\n";
    $last = $line;
}

[download]

-sauoq
"My two cents aren't worth a dime.";

In reply to Re^5: Delete Duplicate Entry in a text file by sauoq
in thread Delete Duplicate Entry in a text file by astronogun

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.