First off, don't use backticks. If you do, the filename passed to open() might be very, very long.

Secondly, you can save a process invocation by doing the grep inline.

  my $file = "/usr/local/apache/logs/access.log.1.gz";
  open(PIPE, "gunzip -dc $file |") or die "gunzip $file: $!";
  while ( <PIPE> ) {
      next if ! m|dd/Mon/yyyy|;

      # massive whatever
  }
  close(PIPE);
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