Thank you for your thoughts. My intent was to produce the OP's requested output w/o doing too much to the original code for the sake of a differentiated learning experience.

I tried your suggestions as follows on the OP's data set:

use Modern::Perl;

my $lastrow = "";

open my $fh, '<', 'fail.txt' or die $!;

while (my $line = <$fh>)
{
    next unless $line =~ /\S/;
    
    if ($line ne $lastrow)
    {
        print $line;
        $lastrow = $line;
    }
}

close $fh;

[download]

Output:

hostname1.com
Gateway FAIL
hostname2.com
Gateway FAIL
Gateway FAIL

[download]

Unless I've misunderstood your re-coding suggestions, they do not produce the OP's desired outcome. (Using say instead of print produces the desired line spacing, but the last string is repeated.)

In reply to Re^4: Delete Duplicate Entry in a text file by Kenosis
in thread Delete Duplicate Entry in a text file by astronogun

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