I know; personally, I tend to do something like

use constant TRUE => 1;
use constant FALSE => !TRUE;
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when I'm going to need those a lot (it's sometimes helpful to be able to communicate that you mean "true value" and not "numerical one").

As for context, you are right; I guess it's a matter of habit. I'd tend to write that hash construction like

my %hash= (
    this => scalar GetThis(),
    foo  => 'bar',
    baz  => 'quux',
);
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That's probably CGI.pm's legacy.. :)