Note that your proposed solution disables buffering. Replace

open my $fh, ">:raw:encoding(ucs-2le):crlf:utf8", $qfn
[download]

with

open my $fh, ">:raw:perlio:encoding(ucs-2le):crlf:utf8", $qfn
[download]

to support buffering.

Also, there doesn't appear to be a need to specify :utf8, so all you need is

open my $fh, ">:raw:perlio:encoding(ucs-2le):crlf", $qfn
[download]