Try this ...
 

use strict;

my ($owo) = "c:/script/owo.txt";

open (OWO, $owo) || die $!;
my (@array, %hash);
foreach (<OWO>) {

    #   push the read line of the file into @array only if it has
    #   not already been encountered
    #
    push (@array, $_) unless (defined($hash{$_}));

    #   store the line as a key of a hash showing that it has been
    #   read previously
    #
    $hash{$_} = 1;
};
close (OWO);

#   Print the unduplicated collection of lines out to the file
#
open (OWO, ">$owo") || die $!;
print OWO join("", @array);
close (OWO);

exit 0;
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Ooohhh, Rob no beer function well without!