$log = "/home/tsec/prototype/logs/extractedlogs/cowrieresult.log";

open(DATA, $log) or die "Can't open '$log': $!";

sub tester()
{
    while(<DATA>){
        ...
    }

    for my $ip (keys %HONEY){
        ...
    }

    for my $data (sort @DATA){
        ...
    }
}

##</code><code>##

my $log = '/home/tsec/prototype/logs/extractedlogs/cowrieresult.log';
open(my $data, '<', $log) or die "Can't open '$log' for reading: $!";
tester($data);
close  $data              or die "Can't close '$log': $!";

sub tester
{
    my ($fh) = @_;

    while (<$fh>) {
        ...
    }
    ...
}