Re^3: Curly braces variable

Same way this is...

use strict 'refs';
${      hello_world } = "hello world";
${ $_ = hello_world } = "hello world";
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They're both basically the same construct, but the syntax on line #2 is a symbolic reference that use strict 'refs' treats as an exception, and allows. The "Not-so-symbolic references" section in perlref documents this.

What it shows I suppose is that the line between symbolic references and hard references is slightly fuzzy.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

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Re^4: Curly braces variable by chromatic (Archbishop) on Apr 30, 2012 at 22:06 UTC
They're both basically the same construct... How do you figure? One of them is a literal identifier and the other is an expression. ... but the syntax on line #2 is a symbolic reference... Yes, because it's not a literal identifier. Compare: `my ${ hello_world } = "hello world";` ... to: `my ${ $_ = hello_world } = "hello world";` Perl complains about the latter because you can't use a scalar dereference as the name of a lexical variable in a declaration. (You don't get to use symbolic references with lexicals anyway, at least without XS.) A quick of the grammar allows you to use a block immediately following the scalar sigil, but you get the runtime error in the `my` op if you have anything other than a literal scalar name here.	[reply] [d/l] [select]

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Re^4: Curly braces variable
by chromatic (Archbishop) on Apr 30, 2012 at 22:06 UTC

They're both basically the same construct...

How do you figure? One of them is a literal identifier and the other is an expression.

... but the syntax on line #2 is a symbolic reference...

Yes, because it's not a literal identifier. Compare:

my ${ hello_world } = "hello world";

... to:

my ${ $_ = hello_world } = "hello world";

Perl complains about the latter because you can't use a scalar dereference as the name of a lexical variable in a declaration. (You don't get to use symbolic references with lexicals anyway, at least without XS.) A quick of the grammar allows you to use a block immediately following the scalar sigil, but you get the runtime error in the my op if you have anything other than a literal scalar name here.

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