You really haven't given all your requirements here, so I apologize if this is a useless suggestion.

I've had success using Data::Dumper or YAML (or its XS replacement YAML::Syck) to dump structures to a file, which is then referenced in the log file. I use a sub that looks something like:

# assumes-> use File::Temp ':POSIX'; for tempnam()
# assumes-> use YAML 'Dump'; (or) use YAML::Syck 'Dump'; for Dump()
sub dump {
    my $message = shift;
    my $structures = scalar @_; # yes, 'scalar' is redudant, but reada
+ble

    # create file in curdir with prefix 'dump.'
    my ($dump_h, $dump_n) = tempnam('.','dump.'); 

    print $dump_h, Dump($_) for @_;
    close $dump_h;
    
    $message.=sprintf '(%d dumped to "%s")', $structures, $dump_n;
}
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And would be called something like:

$logger->fatal( dump('Unable to foo, dumping object $foo_doer.', $foo_
+doer) );
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The log line would look something like:

20070314 15:09 FATAL: Unable to foo, dumping object $foo_doer.(1 dumpe
+d to "dump.foobar1")
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And the file "dump.foobar1" would contain the $foo_doer serialization.

You can equally use Data::Dumper or any other serialization module you prefer using this model.