I decided to unroll that loop to some extent and manually create one of the functions, sha256, as follows:

sub sha256 
{
                my $state = _shaopen('256') or return;
                for (@_) { _shawrite($_, length($_) << 3, $state) }
                _shafinish($state);
                _sha($state);
}
push(@EXPORT_OK, 'sha256');
[download]

For whatever reason, this works fine, but the generation of the function and export does not.

I'll report back if I figure out exactly why this is happening, but for now I am content with having it work with the functions I need hard-coded in.