crazier.pl

use v5.14;
use warnings;

package PackageA {
    # put subs in here and then coderefs passed to PackageA->configure() can use these methods
    # as though they're in the right package
    package PackageA::ConfigurationSubs {
        sub hello {
            say "hello, world";
        }
    }

    sub configure {
        my ($package, $coderef) = @_;
        my ($in) = caller;

        # fetch the symbol table stash for the configuration subs
        my (@symbols) = keys %PackageA::ConfigurationSubs::;

        # copy the methods from PackageA::ConfigurationSubs to the package that
        # called us
        for (my $x = 0; $x <= $#symbols; $x++) {
            no strict 'refs';
            my ($symbol) = $symbols[$x];

            # this is where the subref lives, probably.
            my ($glob) = *{"PackageA::ConfigurationSubs::$symbol"};

            # if there's a subref, localize an alias in the remote package
            local(*{"$in\::$symbol"}) = *$glob{CODE} if (*$glob{CODE});

            # we have to call the coderef in this funky way because otherwise
            # our local()ization of those subs goes away.
            if ($x == $#symbols) {
                $coderef->();
            }
        }
    }
}

package PackageB {
    our (@ISA) = qw(PackageA);

    __PACKAGE__->configure(sub {
        hello(); # calls PackageA::ConfigurationSubs::hello();
    });

    # hello(); <- this would generate an error right here.
}

crazy.pl

use v5.14;
use warnings;

package PackageA {
    sub hello {
        say "hello, world";
    }
}

package PackageB {
    sub configure {
        my ($coderef) = sub {
            hello;
        };

        ...

        # is there a way in the ... for me to call $coderef as though it were declared in
        # PackageA? that is, I want, essentially, $coderef->(); to output "hello, world", not
        # give me an "Undefined subroutine &PackageB::hello" error.
    }
}

Note that I don't really have to call the coderef in the yadda-yadda, and in my eventual real-world case which is more complicated, I'd probably call it either completely outside either package, or inside PackageA.