In-place file editing in Perl 6

inplace.pl

sub inplace($filename, &c) {
    my $f = open $filename;
    # TODO: avoid collision of file names
    my $tmp = "$filename.tmp";
    try {
        my @r := $f.lines.map: &c;
        my $tmp-f = open :w, $tmp;
        $tmp-f.say: $_ for @r;
        $f.close;
        $tmp-f.close;
        unlink $f;
        # TODO: proper escaping
        shell("mv '$tmp' '$filename'");

        CATCH {
            unlink $tmp;
        }
    }
}

inplace('README', *.uc);