a minima; example of the bug

$ cat bug 
sub digest(Str $text) is export {
	my $binary = Q:PIR {
		.local string text
		.local pmc digest

		# Input
		$P0 = find_lex '$text'
		text = $P0

		# Choose the right digest.
		$P1 = loadlib 'digest_group'
		digest = new 'SHA256'

		# Calculate the digest.
		digest.'Init'()
		digest.'Update'(text)
		$S0 = digest.'Final'()

		%r = box $S0
	};
	# Convert to hex.
	return [~] map { sprintf '%02x', .ord }, $binary.comb;
}

say digest('user_name=carl'.split("=")[1]);
say digest('carl');

$ perl6 bug
04f8996da763b7a969b1028ee3007569eaf3a635486ddab211d512c85b9df8fb
69bfe1e6e44821df7f8a0927bd7e61ef208fdb25deaa4353450bc3fb904abd52