use IO::Uncompress::Gunzip;
use IO::Compress::Gzip;

my $gzfile = shift;
open my $fh, $gzfile or die "$gzfile: $!\n";
my $buf = do { local $/; <$fh> };
my ($p1, $p2) = unpack("a4096a*", $buf);
my $ugz = IO::Uncompress::Gunzip->new(\$p1);
$ugz->read(my $gbuf);
$ugz->close;

$gbuf =~ s/.*?(?=^[^%\n])//ms;
my $cgz = IO::Compress::Gzip->new(\ my $z, -Level => 9);
$cgz->syswrite($gbuf);
$cgz->close;

syswrite STDOUT, $z;
syswrite STDOUT, $p2;