In The Unicode Standard, Version 4.0, chillu forms and explicit virama forms are distinguished in text by the use of joiners. For example:
<NA, VIRAMA, ZWNJ> to represent a NA with a visible virama
<NA, VIRAMA, ZWJ> to represent the chillu N
However, the standard is not clear about what <NA, VIRAMA> (without any joiner) represents. Some readers have interpreted the standard such that this sequence represents NA with a visible virama, others have interpreted it to be the chillu N, and yet another possibility is that the sequence does not specify one or the other form (i.e. the rendering system can choose).
The following 5 chillu forms in modern use have been proposed:
MALAYALAM LETTER NN
MALAYALAM LETTER N
MALAYALAM LETTER RR
MALAYALAM LETTER L
MALAYALAM LETTER LL
There is at least one chillu form no longer in modern use, for KA.
If chillu forms are not explicitly encoded, the standard at least needs to be clarified such that