Ho to use a regular expression group reference as hash key

[Andreas Martin]

Hallo !

I'm a Python newbie and I have the following problem:

A hash person={"entry1":"value1","entry2":"value2"}

and I would like to do a substitution with regular expression (an easy
example)
like this:

pat = re.compile(r'(entry1)')
t = pat.sub(person[\1],"something...entry1...something")

I would like to substitute the "entry1" string by the respective hash
element with the group reference \1 as hash key, that is to say
t="something...value1...something".

Similar in Perl:

s/(entry1)/%person($1)/

I hope my problem is understandable.
Thanks