OK, so Dumper output $VAR1 = \''; shows that $self->{_exit} is not a code ref, as expected. You haven't shown the code of Hitachi::Raidcom::exit_routine, but with the error message and Dumper output, it is reasonably clear what is happening.

Your code samples seem to be alternating between exit => \&Hitachi::Raidcom::exit_routine(\%modifier) and _exit => my::module::exit_routine(\%modifier), among other alternatives.

Hitachi::Raidcom::exit_routine(\%modifier) executes the subroutine and yields the value it returns.

&Hitachi::Raidcom::exit_routine(\%modifier) does the same. The & is optional in this case (with the arguments in parentheses) and makes no difference.

\&Hitachi::Raidcom::exit_routine(\%modifier) also runs the subroutine and yields a reference to the value it returns. That's why dumper gives you \''. The \ indicates a reference. In this case, a reference to the empty string.

What will probably work for you is (as AnomalousMonk suggested):

# Setup the log object
my $log = LogSimple->new( logdir => $logdir, logfile => $logfile, logl
+evel => $loglevel, verbosity => $verbosity, exit => sub { Hitachi::Ra
+idcom::exit_routine(\%modifier) } );
[download]

With this initialization, $self->{_exit} should be set to a code reference: to the anonymous sub which does nothing but call Hitachi::Raidcom::exit_routine with the argument \%modifier and return whatever that sub returns. The sub isn't executed immediately. It is executed later, in sub wlog, when the code reference is de-referenced and called. But, I haven't tested...

While this will probably work for you, I will mention closure (just one of many articles on the subject). It is a confusing feature for many, so I suggest you not worry about it immediately, but once you have this working, learn about closure before making too much use of anonymous subroutines accessing lexical variables.