You could probably extract certain key words that you specify, no matter where they appear, but other than that, I don't think you would be able to do what you are asking for, especially when it's an ad you're parsing, which would be in ad-english rather than proper english. It wouldn't be good enough to use:
my @capture = $str =~ /(rabbits|dogs|\d+-\d+)/g;
if the form might change. You would have to make it case insensitive, allow for non-digits and hyphens and parenthesis in the phone number, etc. I don't know what the one-line foreclosure ads tend to look like, but I guess you could have prices that look like telephone numbers (without a $) and encounter other problems.
Maybe you could find some less complete solution, such as identifying when an ad contains a single string of numbers (with possible commas or periods in the proper places) that's preceded by a dollar sign. If you were hoping for some kind of "search-by" feature, maybe you better make it for prices in that format only.
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