my $template = 'iifff';
my $rec_size = template_len($template);
while (1) {
   my $rv = read($fh, my $rec, $rec_size);
   die "$!\n" if !defined($rv);
   last if !$rv;
   die "Premature EOF\n" if $rv < $rec_size;

   my @fields = unpack($template, $rec);
   ...
}