Moderately agree with point 1, only on the grounds that the "-icity" element may pose a stumbling block to some readers (IMHO_and_E, less common and therefore less familiar_and_understandable than "-ness") but am skeptical about recommendation 2:

'Chapt. 3: variables, types and coercion section, it says "assigning to a variable". I assume that should read "assigning type to a variable"?'

Methinks this has serious potential for confusing readers, who've been told that:

"... the sigil of the variable in a declaration determines the type of the variable...."
at "Variable Sigils"

and that...

"Perl 5 variables do not enforce types on their values."
at "Variables, Types, and Coercion"

Perhaps this "potential" arises only from the limits of my own understanding/appreciation, but I must obviously leave that judgement to others.

Suggestion 3 makes excellent sense to me.

Finally (for this post anyway), I find the sections on references, beginning with "Array References" particularly clear. Well done!