my $file = 'path/to/log.dat';
my $out = 'path/to/outfile.txt';
my @lines = ();

open(READ_LOG,"<$file") or die $!;
while(my $line = <READ_LOG>){
  chomp($line);
  push(@lines,$line) if($line !~ /^\s*?$/);
}
close READ_LOG;

my @entries = ();
for(0..$#lines){
  next unless($lines[$_] =~ /\[\d{2}\/\d{2}\/\d{4}/);
  push(@entries,$lines[$_].'; '.$lines[$_+1].'; '.$lines[$_+2]);
}

open(WRITE_OUT,">$out") or die $!;
for(@entries){
  print WRITE_OUT $_,"\n" if(index($_,'is Changed') != -1);
}
close WRITE_OUT;