Hello karlgoethebier,

I’ve been a fan of Const::Fast since I discovered it recently in the Perl Advent Calendar 2017. But constant does have one important advantage over Const::Fast: it is applied at compile time, whereas Const::Fast takes effect only at run time. So, in this respect, Const::Fast suffers from the same limitation, identified by choroba, as the &CONSTANT syntax for the constant pragma — the constant isn’t inlined:

 0:59 >perl -Mstrict -MData::Dump -MConst::Fast -we "use constant A =>
+ 12; const our $B => 13; my %h = ( (A) => 'twelve', $B => 'thirteen')
+; dd \%h;"
{ 12 => "twelve", 13 => "thirteen" }

 0:59 >perl -Mstrict -MO=Deparse -MData::Dump -MConst::Fast -we "use c
+onstant A => 12; const our $B => 13; my %h = ( (A) => 'twelve', $B =>
+ 'thirteen'); dd \%h;"
BEGIN { $^W = 1; }
use strict;
use Data::Dump;
use Const::Fast;
use constant ('A', 12);
&const(\our $B, 13);
my(%h) = (12, 'twelve', $B, 'thirteen');
dd(\%h);
-e syntax OK

 0:59 >
[download]

(AFAICT, this also makes Const::Fast unsuitable in situations where one wants to write code like this:

use constant DEBUG => 0;
...
perform_some_debugging_operation() if DEBUG;
...
[download]

and have the compiler remove the expensive operation when it sees that DEBUG is false.)

Update: Changed perform_expensive_debugging_operation() to perform_some_debugging_operation(), because, as Eily pointed out in a private message, the cost of the operation is irrelevant if DEBUG (or $DEBUG) is false.

Cheers,