So, it seems that my wishlist #1 is shared by many monks. With help from clkao, I've just implemented it. To wit:

use Digest--perl5;

my $cxt = Digest.SHA1;
$cxt.add('Pugs!');

# This prints: 66db83c4c3953949a30563141f08a848c4202f7f
say $cxt.hexdigest;
[download]

If you want to play along, build the Pugs from trunk, and run Makefile.PL with the PUGS_EMBED environment variable containing "perl5". There's many rough edges, but they will be fixed in short order. Tests and suggestions welcome!