Ah - something like this:

use File::Find;
use XML::Simple;
use strict;
use warnings;

my $root = shift or die "Usage: $0 rootdir\n";

my %tree;

find( 
sub 
{
    #print "$File::Find::name\n";
    my @path = split m,/,, $File::Find::name;
    my $tree = \%tree;
    $tree = (($tree->{'dir'} ||= {})->{shift @path} ||= {})
        while @path > ( -d _ ? 0 : 1 );
    @path and # it's a file
        push @{ $tree->{'file'} ||= [] }, shift @path;
},
$root
);

print XMLout( \%tree );
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