Your assert function won't be able to see lexical variables.

my $x = 42;
assert '$x > 40';   # assertion fails,
                    # because eval can't see $x
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Better is to write assert so that it takes a code ref...

sub assert (&) {
   require Carp;
   (shift)->() ? 1 : Carp::croak('Assertion failed')
}

my $x = 42;
assert { $x > 40 };   # assertion ok
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Also, I'd recommend giving your pseudo-constants TRUE, FALSE and EXIT_SUCCESS an empty prototype - i.e. () - and not using the return keyword in them. This allows the Perl compiler to treat them as real constants - inlining them into code that calls them. And if will solve your problems that lead them to occasionally needing to be called with a leading &.

sub TRUE         () { 1 }
sub FALSE        () { 0 }
sub EXIT_SUCCESS () { TRUE }
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