The whole point of ":crlf" mode is that, when you say "\n" (LINE_FEED) in your code, perl interprets that to mean "newline event", which by definition comes out as "CARRIAGE_RETURN LINE_FEED" (hence the name ":crlf" mode); when you use this mode, you would never explicitly print a "\r" (carriage return) to such a file handle, unless you really want an "extra" carriage return in the output.

OTOH, you can leave off ":crlf", explicitly print "\r" wherever/whenever you want, and not get them added automatically when you print "\n".

Since you seem fixated on explicitly printing the carriage returns yourself, and not having them added automatically to every line feed that you print, just leave out ":crlf".

Based on the tests you've shown, it is essential in any case to make sure the mode begins with ":raw". Without this, the default (actually implicit) ":crlf" mode will somehow be treated in the wrong sequence relative to the ucs2le mode, and the "crlf" sequence does not get converted to a valid sequence of two 16-bit unicode characters. In terms of the code you're showing:

## instead of this:

open( my $fh, ">:raw:encoding(ucs2le):crlf", "testa.plp" );
print $fh "\N{CARRIAGE RETURN}\N{LINE FEED}";
close $fh;

## you want either this:

open( my $fh, ">:raw:encoding(ucs2le)", "testb.plp" );
print $fh "\N{CARRIAGE RETURN}\N{LINE FEED}";
close $fh;

## or this:

open( my $fh, ">:raw:encoding(ucs2le):crlf", "testc.plp" );
print $fh "\N{LINE FEED}";  # :crlf adds CARRIAGE RETURN for you
close $fh;
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Just for the sake of parsimony and lower probability of screwing things up, I'd prefer the last approach, personally.