Perl constant array

Or remove the curly braces as the docs show :-

  1 use strict;
  2 use constant COLUMNS => qw/ TEST1 TEST2 TEST3 /;
  3 
  4 my @attr = (COLUMNS);
  5 print @attr;

which gives :-

 % perl test.pl
TEST1TEST2TEST3

Your code actually defines two constants COLUMNS and TEST2 :-

use strict;
use constant { COLUMNS => qw/ TEST1 TEST2 TEST3 /, };

my @attr = (COLUMNS);
print @attr;
print TEST2

and gives :-

% perl test.pl
TEST1TEST3

Use a + to signify that it's a contant.

use constant {
  COLUMNS => [qw/ TEST1 TEST2 TEST3 /],
};

print @{+COLUMNS};

The + is a hint to the interpreter that the constant is actually a constant, and not a bare word. See this reply for more details.

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