My code:
chdir($archivedir);
my ($WRITEME);
my $program= "| \"$bindir/cpio\" -o -O arch.cpio.new ";
my $pid = open( $WRITEME, $program);
binmode $WRITEME; <<<<<<<<<<<<<<<<<<<<<<<<<<<<<solution
foreach my $f (@filelist){print $WRITEME "$f\n";}
close($WRITEME);