[Python] Return elements from a list that match a pattern

I have a list of words as below:

STR = ['aa', 'dffg', 'aa2', 'AAA3']


I want to get a list of elements from the above list that match a string:

to_match = 'aa'


I tried the code below:

import re
[re.findall(to_match, iWord) for iWord in STR]
# [['aa'], [], ['aa'], []]


However, I wanted to get a list like ['aa', 'aa2', 'AAA3'].

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