open(my $fh, '-|', 'gunzip', '-c', '--', $input_file)
   or die("Can't start gunzip: $!\n");

while (!eof($fh)) {
   defined($_ = <$fh>)
      or die("Error reading from gunzip: $!\n");

   ...
}

close($fh)
   or die("Can't close gunzip: $!\n");

($? & 0x7F) and die("gunzip died from signal ", ($? & 0x7F), "\n");
($? >> 8)   and die("gunzip exited with error ", ($? >> 8), "\n");