#
# Instead of @data, one could assign separate variables
# like this:
#
# ($user,$id,$line,$pid,$type,$exit_1,$exit_2,$tv_1,
#  $tv_2,$session,$pad_1,$pad_2,$pad_3,$pad_4,$pad_5,
#  $syslen,$host) = unpack(...);
#
open(FD,"</var/adm/wtmpx") or die;
my $wtmpx;
my @data;
while(read(FD,$wtmpx,372)) {
  @data =  unpack('A32 A4 A32 l s ss xx ll l lllll s A257', $wtmpx);
  # Do things!
}
close(FD);