in reply to Parsing Pattern Question

Parent post as it stood when I replied
H, Perl newb here.... I have an application log I'm trying to retrieve a specific sequence of 4 lines
from(event1, event2,event3, event4 - discarding any duplicates in between).
I've already filtered the log to get all occurances the four lines I want
but I don't know how to pull out the four lines when they happen sequentially.
EX:

09:12:50:861 EVENT1 #Don't want this line
09:13:09:467 EVENT1 #Don't want this line
09:13:09:837 EVENT1
09:13:38:059 EVENT2
09:14:03:115 EVENT3
09:14:04:076 EVENT4
09:14:11:376 EVENT1
09:14:34:049 EVENT2
09:14:34:990 EVENT3
09:14:34:990 EVENT3 #Don't want this line
09:14:34:990 EVENT4

I then need to do a time calculation between each of the four events (I can do this part....I just can't
figure out how to pull out the four lines I want everytime they appear in the sequential order I am looking for)
Can anyone help?
Thanks!
my $last;
my @history;
my $expect = 1;
while (<>) {
    chomp;

    my ($num) = /EVENT(\d+)/
        or next;  # Ignore bad input.

    next if defined($last) && $last eq $_;
    $last = $_;

    if ($num == 1 || $num != $expect) {
        @history = ();
        $expect = 1;
    }

    if ($num == $expect) {
        push @history, "$_\n";
        if ($expect++ == 4) {
            print(@history);
            @history = ();
            $expect = 1;
        }
    }
}

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Update: Handle duplicates as requested.

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