Simplify the following text for a Grade 7 native English-speaking person.
Original: When this particle is absent , the infinitive is said to be a bare infinitive ; when it is present , it is generally considered to be a part of the infinitive , then known as the full infinitive ( or to-infinitive ) , and there is a controversy about whether it should be separated from the main word of the infinitive ( see Split infinitive ) .
Simplified: perfect infinitive e.g. to have written