You can use refs instead of copying arrays, and hashes to make the code more readable for humans.

The code below is syntactically correct but not tested.

use Data:Dumper;
...
while (my $event = $sth->fetchrow_hashref()) {
    push @recordset, $event;
};
$sth->finish;


for (my $i=0; $i<@recordset; $i++) {
    if ($recordset[$i]->{DIRECTION} eq "exit") {
        for (my $j=$i+1; $j<@recordset; $j++) {
            if ($recordset[$i]->{OCR} == $recordset[$j]->{OCR}) {
                undef $recordset[$j];
            }
        }
        undef $recordset[$i];
    }
}

for my $row ( @recordset ) {
    print Dumper($row) . "\n" if defined $row;
}
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