From zefram@fysh.org

"\x[111c2,111c4]".chars
2

The above is erroneous​: these two codepoints make up a single extended
grapheme cluster. U+111c2 "Sharada sign jihvamuliya" has the property
Indic_Syllabic_Category=Consonant_Prefixed, which per UAX #​29 makes it a
Grapheme_Cluster_Break=Prepend, which means that it falls under rule GB9b,
so there should not be an extended grapheme cluster break following it
(except when what follows is a control character or end of text).

Strangely, the rule about Prepend characters doesn't seem to be being
entirely ignored. It is taking effect if the following character is
also a Prepend​:

"\x[111c2,111c3]".chars
1

-zefram

From @samcv

We did not support Prepend until a month or two ago when when I added it. Currently it only works when it comes before a character that has property `NFG_QC = 0` (not an official Unicode property).

The plan is to add support for saving state when putting codepoints into graphemes and improving some other things.

The RT System itself - Status changed from 'new' to 'open'

From @samcv

This has been fixed as of MoarVM/MoarVM@78b60512

in MoarVM. Yay.

@samcv - Status changed from 'open' to 'resolved'