use PerlIO::gzip;
open my $out, ">:gzip", "tst.gz";
print $out "111111111111111111111111\n" x 100;
close $out;
open my $out, ">>:gzip", "tst.gz";
print $out "222222222222222222222222\n" x 100;
close $out;

open my $in, "<:gzip", "tst.gz";
print while <$in>;
close $in;