Windows + Strawberry Perl + Gnuplotでパイプ処理の場合に文字化けする例

sample.pl

#!/usr/bin/perl

use strict;
use warnings;
use utf8;

use File::Temp qw(tempfile);

my $xlabel = "時刻 [s]";
my $ylabel = "振幅 [m]";


my ($tgnuplot, $filename) = tempfile();
binmode $tgnuplot, ':utf8';
print $tgnuplot <<__EOM__;
set terminal pdfcairo noenhanced
set output 'sample_tempfile.pdf'
set xlabel '$xlabel'
set ylabel '$ylabel'
set xrange [-2*pi:2*pi]
plot sin(x)
unset output
__EOM__
close $tgnuplot;
system "pgnuplot $filename";


open my $pgnuplot, '|-:utf8', 'pgnuplot' or die $!;
print $pgnuplot <<__EOM__;
set terminal pdfcairo noenhanced
set output 'sample_pipe.pdf'
set xlabel '$xlabel'
set ylabel '$ylabel'
set xrange [-2*pi:2*pi]
plot sin(x)
unset output
__EOM__
close $pgnuplot;
exit;

パイプを使ったとき、振幅と[m]の間にEのような文字が入る。