use warnings;
sub import {
- $^H{myint} = 1;
+ $^H{"myint/in_effect"} = 1;
}
sub unimport {
- $^H{myint} = 0;
+ $^H{"myint/in_effect"} = 0;
}
sub in_effect {
my $level = shift // 0;
my $hinthash = (caller($level))[10];
- return $hinthash->{myint};
+ return $hinthash->{"myint/in_effect"};
}
1;
is encapsulated into the routine C<in_effect()>, which takes as parameter
the number of call frames to go up to find the value of the pragma in the
user's script. This uses C<caller()> to determine the value of
-C<$^H{myint}> when each line of the user's script was called, and
+C<$^H{"myint/in_effect"}> when each line of the user's script was called, and
therefore provide the correct semantics in the subroutine implementing the
overloaded addition.
+=head1 Key naming
+
+There is only a single C<%^H>, but arbitrarily many modules that want
+to use its scoping semantics. To avoid stepping on each other's toes,
+they need to be sure to use different keys in the hash. It is therefore
+conventional for a module to use only keys that begin with the module's
+name (the name of its main package) and a "/" character. After this
+module-identifying prefix, the rest of the key is entirely up to the
+module: it may include any characters whatsoever. For example, a module
+C<Foo::Bar> should use keys such as C<Foo::Bar/baz> and C<Foo::Bar/$%/_!>.
+Modules following this convention all play nicely with each other.
+
+The Perl core uses a handful of keys in C<%^H> which do not follow this
+convention, because they predate it. Keys that follow the convention
+won't conflict with the core's historical keys.
+
=head1 Implementation details
The optree is shared between threads. This means there is a possibility that