Using XML::Twig you create and parse the twig with:

my $t= XML::Twig->new();
$t->parse( $content);
[download]

You can get all the audio elements by doing: my @audio= $twig->descendants( 'audio') (I'll let you figure out how to get all the goto elements ;--)

You can then access the src attribute using $elt->att( 'src')