Without more details of what you're actually doing with these, I don't see anything particularly wrong with it. Handing an object as a parameter to another object is just fine -- things of that sort are frequently refered to as following a "delegation" pattern -- though that does have some specific semantics. Some useful references include:

• Often Overlooked OO Programming Guidelines
• Inheritance vs Delegation: pros and cons
• Law Of Demeter (from Perl Design Patterns, which is itself a good resource)

Underscore parameters (and subs) have the convention of indicating private, but there's no real reason you can't deviate as needed. If it helps you in your coding, but you want to be more consistent for users, you might take "object1" as an argument to new but store it as _object1 internally to help distinguish in your coding.