text -> extracted list of words

Hi all,

I'm looking for a way to extract all words out of a text-field.
Delimiter: all except alphanumeric + dash + underscore

e.g.

SELECT extr('Hello World. This is a foo_bar test','-_a-zA-Z0-9');
'Hello'
'World'
'This'
'is'
'a'
'foo_bar'
'test'
7 rows

Of course I could do this in the app but in the db it would be much handier.
Is there already such a function ?

TIA
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