#!/usr/bin/perl

use strict;
use RTF::Writer;

die "Usage: $0  file.txt\n  (this will create file.rtf)\n"
    unless ( @ARGV and $ARGV[0] =~ /\.txt$/ and -f $ARGV[0] );

# input file is expected to be utf8

open( I, "<:utf8", $ARGV[0] ) or die "$ARGV[0]: $!";
my $utf = do { local $/; <I> };  # slurp it

# here's the magic part: replace each wide character with
# "\uN\5f", where "N" is the decimal numeric codepoint:

$utf =~ s/([^[:ascii:]])/sprintf("\\u%d\\'5f",ord($1))/eg;

( my $out = $ARGV[0] ) =~ s/txt$/rtf/;

my $rtf = RTF::Writer->new_to_file( $out );

my @pars = split( /\n+/, $utf );
$rtf->prolog( title => $out );
for my $par ( @pars ) {
    $rtf->paragraph( \$par );  # need to pass $par by reference
}
$rtf->close;