Perhaps the following looks pathological, but I have code which needs to use hash keys which may later change in value. It made sense to utilize a layer of indirection through constants. 
#!/usr/bin/perl

use strict;
use warnings;

use constant {
    FOO => 'foo',
    BAR => 'bar'
};

my %mapping = (
    @{[FOO]} => 0,
    @{[BAR]} => 1
);

for my $k (keys %mapping) {
    print "$k\t$mapping{$k}\n";
}

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This code appears to work given that the output is: 
bar     1
foo     0

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I understand that constants are implemented as subroutines which return the value assigned, but I don't understand the syntax. What is the @{[...]} syntax doing? I know that it isn't an array, and ultimately the subroutine has to be called before constructing the reference (?) into the hash, but I'm only guessing. Can you elucidate what the syntax is really specifying to the Perl interpreter?

Thanks.

In reply to explanation of constant syntax? by Anonymous Monk

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