Кажется, работает для меня:
C:\Documents and Settings>cat a.pl
$sectionfilename = "a.txt";
$section = "Hello \x{263A}!\n";
open (OUT, ">$sectionfilename");
binmode(OUT, ":utf8");
print OUT $section;
close OUT;
C:\Documents and Settings>perl a.pl
C:\Documents and Settings>file a.txt
a.txt: UTF-8 Unicode text, with CRLF line terminators
Но когда я изменяю текст для записи:
$section = "Hello";
и запустить:
C:\Documents and Settings>perl a.pl
C:\Documents and Settings>file a.txt
a.txt: ASCII text, with no line terminators