Escaping { $ @ % in strings

[Thom Boyer]

S02 provides this example for treating curlies literally in a quoted string:

qq:!c Here are { $two uninterpolated } curlies;

But can I escape them with a backslash? I was surprised that I couldn't 
find anything in S02 which said either yes or no. Perhaps this falls 
under the heading of anything not specifically defined in the synopses 
acts just like it did in Perl 5, and I should just shut up.


In the description of the :q (aka :single) adverb, there is mention of 
the fact that you can escape the quoting character, as in


Q :q The ubiquity of \air quotes\ is really annoying to me;

and the description of :b (aka :backslash) indicates that it activates 
the usual substitutions on \a, \b, \t, \n, \f, \r, and \e,


Q :b Here's a BEEP \a and a newline \n;

but I can't find any discussion of whether \p is legal (presumably 
identical to p) or lexically illegal (unrecognized escape sequence in 
string literal). And in that example, by p I mean any character p for 
which S02 doesn't define the meaning of \p.


In particular, there's no mention of whether \ can be used to escape $, 
@, %, , or {. I would _assume_ that


Here are \{ $two uninterpolated \} curlies;

means the same as the first example, above, but I can't find anything 
that says so.


So, I would hope that

$fruit = 'apple';
$number = 7;
$money = 'peso';
say set A = \{ $fruit, {$number+1}, \$money \};

actually says

set A = { apple, 8, $money }

Does it? And, do I really need to backwhack the final (closing) curly?

say set A = \{ $fruit, {$number+1}, \$money };

Re: Escaping { $ @ % in strings

[Larry Wall]

On Thu, Feb 14, 2008 at 03:51:21PM -0700, Thom Boyer wrote:
 S02 provides this example for treating curlies literally in a quoted string:

 qq:!c Here are { $two uninterpolated } curlies;

 But can I escape them with a backslash? I was surprised that I couldn't 
 find anything in S02 which said either yes or no. Perhaps this falls under 
 the heading of anything not specifically defined in the synopses acts just 
 like it did in Perl 5, and I should just shut up.

Well, it ends up being the same as Perl 5 in the degenerate cases, but
that's far from an adequate reason to shut up.

 In the description of the :q (aka :single) adverb, there is mention of the 
 fact that you can escape the quoting character, as in

 Q :q The ubiquity of \air quotes\ is really annoying to me;

 and the description of :b (aka :backslash) indicates that it activates the 
 usual substitutions on \a, \b, \t, \n, \f, \r, and \e,

 Q :b Here's a BEEP \a and a newline \n;

 but I can't find any discussion of whether \p is legal (presumably 
 identical to p) or lexically illegal (unrecognized escape sequence in 
 string literal). And in that example, by p I mean any character p for 
 which S02 doesn't define the meaning of \p.

The default depends on whether the basic intent is double or single
quoting, basically.  See my last S02 changes.

 In particular, there's no mention of whether \ can be used to escape $, @, 
 %, , or {. I would _assume_ that

 Here are \{ $two uninterpolated \} curlies;

 means the same as the first example, above, but I can't find anything that 
 says so.

Does now.  :)

 So, I would hope that

 $fruit = 'apple';
 $number = 7;
 $money = 'peso';
 say set A = \{ $fruit, {$number+1}, \$money \};

 actually says

 set A = { apple, 8, $money }

 Does it?

Well, actually, it says:

Variable $fruit requires predeclaration or explicit package name

:)

 And, do I really need to backwhack the final (closing) curly?

 say set A = \{ $fruit, {$number+1}, \$money };

There it is optional, because } does not cause interpolation.
(Though if the delimiters were curlies, the opener and closer would
have to be backslashed the same, to avoid throwing off the bracket
counter.)  In any case, double quoting removes the backslash from
any non-alphanumeric character.  Single quoting tends to preserve them.

Larry