Use a hash. Something like the following 


# opening of files etc.

my %users = ();


while ($line = <errlog>) {
    chomp $line;
    next unless ($line =~ /Login succeeded/);
    $users{(split / /, $line)[6]} ||= 1;
}

foreach (sort keys %users) {
   print LOGINF $_, "\n";
}

# closing fhs etc

[download]
This is untested.

NB: consider using lexical filehandles.

hth,

regards,
tomte

An intellectual is someone whose mind watches itself.
-- Albert Camus

In reply to Re: array processing by Tomte
in thread array processing by Anonymous Monk

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