Does this do what you want?

#!/usr/bin/perl

use strict;
use warnings;
use v5.10;
sub YadaYada {
    say "YadaYada";
     };
use Xyzzy (\&YadaYada);

say "Executing ".__PACKAGE__;
INIT { say __PACKAGE__."::INIT"; };
END { say __PACKAGE__."::END"; };
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package Xyzzy;

use Data::Dumper;
use strict;
use warnings;
use v5.10;

my $external;
sub import {
    shift;
    $external=$_[0];
     };
say "Executing ".__PACKAGE__;
INIT { say __PACKAGE__."::INIT"; $external->(); };
END { say __PACKAGE__."::END"; };
     1;
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yields

Executing Xyzzy
Xyzzy::INIT
YadaYada
main::INIT
Executing main
main::END
Xyzzy::END
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