Help retrieving only Portuguese words from a file

Hello,

And some words exist in Portuguese, Spanish and English, the three
languages of the problem. For instance, "animal". I don't think this
problem can be solved, but a dictionary search would tell if it is a
Portuguese word, which it is.

Is there any structure to the text? If it has complete paragraphs in
one of the three languages then you can probably make a better guess
of the language of the paragraph from the presence of key words. I
wonder if some of the code for detecting spam can help you here...
Train it on some known Portuguese, Spanish, and English text...

 If its just a stream of words in one of the languages in a random
order then it is difficult or impossible.

Barry