You can use PerlIO layers to do that.

PerlIO::via::gzip provides on the fly data compression (and it uses IO::Compress::Gzip under the hood).

# untested!

sub writefile {
    my($opts) = @_;

    open my $fh, '>', $opts->{filename} or die $!;
    binmode($fh, ':via(gzip)') if $opts->{'gzip'};
    binmode($fh, ':utf8');

    print $fh $opts->{'data'};
    $fh->close;
}
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