Constants using the constant pragma need not be scalars, they can be arrays lists too: 
use Data::Dumper;
use constant MSG_DATA => { foo => 1 },
                         { bar => 2 },
                         { baz => 3 };

for my $msg (MSG_DATA) {
    print Dumper $msg;
}

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Use [ MSG_DATA ] elsewhere in the code if you need to use the list as an reference.

Incidentally, this feature is the source of many accidental bugs with constant: 

use constant FOO => "xyz",
             BAR => "def",
             BAZ => "abc";

# FOO returns qw/xyz BAR def BAZ abc/
# BAR and BAZ aren't defined as constants

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The programmer probably meant to declare three constants, not one: 
use constant { FOO => "xyz",
               BAR => "def",
               BAZ => "abc" };

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blokhead

In reply to Re: looping over constant data structure references by blokhead
in thread looping over constant data structure references by leriksen

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