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Re: Embedding code in qq{}?

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In article <1fjg39-qnv2.ln1@anubis.morrow.me.uk>,
Ben Morrow  <ben@morrow.me.uk> wrote:
>
>Quoth tmcd@panix.com:
>> In article <87limyk471.fsf@Gmail.com>, XeCycle  <XeCycle@Gmail.com>
>> wrote:
>> >Is it possible to use something like "${1+2}" -> "3"?
>> 
>> You made it clear in the rest of the article (which I trimmed) that
>> you were thinking about the right-hand side of a s///.  It turns out
>> that, in string contexts in general, you can do it.
>> 
>> Short answer:
>>     ${\(1+2)}
>
>If you must do this, then @{[...]} is clearer, since in both cases
>the internal code is evaluated in list context.

Both are in a scalar context, I think.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#! /usr/bin/perl
use strict;
use warnings;

sub tester {
    if (wantarray) {
        print "array context\n";
        return [ 11, 12, 13 ];
    } else {
        print "scalar context\n";
        return \(22);
    }
}

print "scalar: ", ${tester()}, "\n";
print "array: ", @{tester()}, "\n";
exit 0;

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Output:

$ perl local/test/088.pl
scalar context
scalar: 22
scalar context
Not an ARRAY reference at local/test/088.pl line 16.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In retrospect, that makes sense.  The ${...} and @{...} sigils want
the block to return *one reference*, which is a scalar, so why not
evaluate in scalar context?

The advantage I see for @{[BODY]} even for a scalar is that you just
need to have BODY evaluate to a normal scalar. [...] takes care of
changing it to the required reference, and @{...} converts it to an
array of one element, which within a string and a list context
evaluates to the original scalar (though of course you have to be
careful in a scalar context not to blindly use it and get the length,
1).

However, ${BODY} has to have the BODY evaluate to a reference to a
scalar, which may make \ have to spring up throughout.

-- 
Tim McDaniel, tmcd@panix.com

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Thread

Embedding code in qq{}? XeCycle <XeCycle@Gmail.com> - 2012-03-18 10:56 +0800
  Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-17 23:04 -0400
    Re: Embedding code in qq{}? XeCycle <XeCycle@Gmail.com> - 2012-03-18 12:14 +0800
  Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-18 07:07 +0000
    Re: Embedding code in qq{}? Ben Morrow <ben@morrow.me.uk> - 2012-03-18 08:37 +0000
      Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-18 22:28 +0000
        Re: Embedding code in qq{}? merlyn@stonehenge.com (Randal L. Schwartz) - 2012-03-18 16:18 -0700
          Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-19 02:21 +0000
            Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-19 00:14 -0400
              Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-19 06:42 +0000
                Re: Embedding code in qq{}? Ben Morrow <ben@morrow.me.uk> - 2012-03-19 16:40 +0000
        Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-18 19:29 -0400
    Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-18 15:24 -0400
      Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-18 22:33 +0000
        Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-18 19:24 -0400
          Re: Embedding code in qq{}? Ben Morrow <ben@morrow.me.uk> - 2012-03-19 00:49 +0000
            Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-18 22:05 -0400
          Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-19 02:55 +0000
            Re: Embedding code in qq{}? Uri Guttman <uri@stemsystems.com> - 2012-03-19 00:12 -0400
              Re: Embedding code in qq{}? tmcd@panix.com (Tim McDaniel) - 2012-03-19 07:00 +0000
                Re: Embedding code in qq{}? Ben Morrow <ben@morrow.me.uk> - 2012-03-19 16:43 +0000

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