Here is an example to get you started, based upon Mojo::DOM:

use strict;
use warnings;
use feature 'say';

use Mojo::DOM;

my $html = '<span class="details-title-text">
  <strong>$8.39</strong>
</span>
<span class="details-title-text">
  <strong>$1</strong>
</span>
<div>
  <strong>do not find me</strong>
</div>
<span>
  <strong>find this</strong>
</span>';

my $dom = Mojo::DOM->new( $html );

for my $element ($dom->find('span strong')->each) {
  say $element->text;
}
[download]

output:

$8.39
$1
find this
[download]

I'll leave determining if the element text is a price as an exercise for you.