This is nothing but putting a word between To and the verb following. Puting a word inbetween TO and a following verb means you have split the infinitive.
In the past, it was thought as wrong but now-a-days this is used in the grammar. This is now a days common tendency to put adverbs of degree before the verb which is widely spread now a days like "TO FULLY AGREE"
We can even split infinitives with negative words like:
1."I decided not to do something."
2."He called him to call his Aunt."
3."She wish to gradually get rid of the topic"
4."You will have to try harder not to accidentally forget that poem."
This way we can split the infinitives which has strong accent on the word. This type of splitting is mainly used in the Rhymes.