Assuming that the entries in the log file are ordered by time which is the case in your test data and that you only want to keep the last entry of a particular event, the following would work.

#!/usr/bin/perl -w

use strict;

my %log;

foreach(<DATA>) {
  chomp;
  if(!/^$/){
    /.+(EVENT\d)/;
    $log{$1} = $_;
  }
}

print map { "$log{$_}\n" } sort keys %log; 

__DATA__
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 #Don't want this line
09:14:34:990 EVENT3
09:14:34:990 EVENT4

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In reply to Re: Parsing Pattern Question by arun_kom
in thread Parsing Pattern Question by dlcasey

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