It's built into the perl executable itself: 
BEGIN { %Foo::FIELDS = qw(a 1 b 1) };
my Foo $x = {};
$x->{c} = 1; # compile-time error

[download]
fields.pm just populates the field hash

Dave.

In reply to Re^4: Recap: The Future of Perl 5 by dave_the_m
in thread Recap: The Future of Perl 5 by Ovid

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