found what i wanted:

my $collection =  Mojo::DOM->new($args->{'body'})->find('iframe');
my @links;
my $cpt = 0;
foreach (@$collection) {
    $links[$cpt] = $_->{src};
   print STDERR Dumper($_->{src}); # access elements of iframe with ->
   $cpt++;
}
[download]

thanks you u'r help