One technique you can use is a "scope guard"; an object which goes out of scope when a scope is exited. When it goes out of scope, its reference count drops to zero and its DESTROY method is called:

# slave.pl:
use 5.014;
use warnings;
my $CleanExit = 0;
{
    package My::ScopeGuard;
    sub DESTROY {
        return if $CleanExit;
        say 'cleaning up slave.pl';
    }
}

# this is the object that will go out of scope
my $guard = bless {}, 'My::ScopeGuard';

say 'doing something';
die "Oh Noez";

# or if everything works fine:
$CleanExit = 1;
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Now we can test it likes this:

$ perl -wE 'do "slave.pl"; say "Back in master"'
doing something
cleaning up slave.pl
Back in master
[download]

You can see that the cleanup happens before the the rest of the calling code.