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Postings from October 2014
Perl v5.20 deprecates the use of control characters as single character
variables. What actually raises a warning are the ASCII C0 controls and
DEL. rjbs says he meant to have the C1 [\x80-\x9f] controls also
deprecated, but that's not what got implemented.
My view is that we shouldn't have invisible variable names; hence
anything that doesn't have a graphic has no business being in a variable
name.
I think we should deprecate any non-graphics as single character
variables. In the 0-255 range, that merely adds the C1 controls,
no-break space, and the soft-hyphen to the list that currently warn.
The documents don't state it, but SPACE currently can't be a single
character variable name, because it is used by the parser/lexer to
delimit tokens.
I'm told that a common single variable name is ${£} U+A3. The rules
actually currently are that if a program is UTF-8 encoded, a non-ASCII
single character variable must follow the rules for any identifier,
which means essentially that it be an alphabetic (there are a few alphas
that can't be an identifier, but the basic rule holds). This means that
currently a UTF-8 program can't use £. It seems to me that it does no
harm to allow currency symbols be single-character variables in general,
such as the EURO SIGN, but I don't think we should get into allowing
other symbol types or punctuation or numbers as single char variable
names, without evidence of need.
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