Update:Mirod points out that this trick will only work if your version of XML::Simple is using XML::Parser as it's underlying parser. If you have/are using SAX as the underlying Parser - ignore this:). Thanks for the heads-up Mirod++.

XML::Simple has a parseropts option which allows you to pass XML::Parser options through to the XML::Parser instantiated by XML::Simple. One of the XML::Parser options is Handlers=> [ Event=>\&handler, ...].

By using this to register your own handlers you can get your own code called--with salient information as to what is being processed--as XML::Parser processes your document.

The problem is that doing so overrides the XML::Parser::Tree style handlers used by XML::Simple. However, these handlers conform to a standard naming convention and it is easy to use perl's goto &func; form of goto, to invoke these standard handlers from your own once you have finished tracing the info.

The PoC code below produces this output while successful parsing the emebedded example XML.

c:\test>231115
Init:
Start: config logdir /var/log/foo/ debugfile /tmp/foo.debug
Char:
Char:
Start: server name sahara osname solaris osversion 2.6
Char:
Char:
Start: address
Char: 10.0.0.101
End: address
Char:
Char:
Start: address
Char: 10.0.1.101
End: address
Char:
Char:
End: server
Char:
Char:
Start: server name gobi osname irix osversion 6.5
Char:
Char:
Start: address
Char: 10.0.0.102
End: address
Char:
Char:
End: server
Char:
Char:
Start: server name kalahari osname linux osversion 2.0.34
Char:
Char:
Start: address
Char: 10.0.0.103
End: address
Char:
Char:
Start: address
Char: 10.0.1.103
End: address
Char:
Char:
End: server
Char:
End: config
Final:
c:\test>
[download]

The code: (Update:simplified option setting code)

#! perl -sw
use strict;
use XML::Simple;
use Data::Dumper;

my @handlers = qw[
    Init Start Char Proc Comment 
    CdataStart CdataEnd End Final
];

for my $handler ( @handlers ) {
    eval "sub $handler\t{ print qq[\$handler: \@_[1 .. \$#_]\\n]; goto
+ \&XML::Parser::Tree::$handler; }";
}
my %handlers = map{ $_ => eval "\\&$_" } @handlers;

my $xml = XML::Simple->new();
my $config = $xml->XMLin( \*DATA, 
    parseropts => [ Handlers => \%handlers, ] 
);

#print Dumper $config;

__DATA__
<config logdir="/var/log/foo/" debugfile="/tmp/foo.debug">
    <server name="sahara" osname="solaris" osversion="2.6">
        <address>10.0.0.101</address>
        <address>10.0.1.101</address>
    </server>
    <server name="gobi" osname="irix" osversion="6.5">
        <address>10.0.0.102</address>
    </server>
    <server name="kalahari" osname="linux" osversion="2.0.34">
        <address>10.0.0.103</address>
        <address>10.0.1.103</address>
    </server>
</config>
[download]

For more information on what handlers you can override, and what information is passed to them see the XML::Parser pod. (or source).

I might make a package out of this idea if anyone is interested.