By that criteria Matz is a Perl hacker in the same way that he is a Smalltalk hacker. And Larry Wall is a Lisp, Ruby and Python hacker.
I'm not doubting that Larry Wall understands Lisp, Ruby and Python. He certainly understands them well enough to know what the major datatypes and basic syntax are. He might need to refer back to references for details, but he certainly could program in them. He even knows them well enough that he probably has ideas about how he might implement them if he wanted to. But for some reason you don't hear much about the masses of code that Larry chooses to write in those languages.
Conversely I don't doubt that someone of Matz' level would be very competent in Perl almost immediately upon learning the language. After all he already knows how to think and organize his thoughts, he merely needs to learn how to express those thoughts in Perl. However what he means by "reorganized the features in Perl into class library" is that he designed a class library that provided datatypes corresponding to Perl's major datatypes. He then wrapped his method calls in enough syntactic sugar so that some of the shortcuts would look similar. He didn't try to reproduce Perl, he just tried to make (without compromising his OO framework) it possible for people to script problems like they would in Perl.
The knowledge of Perl which is implied is on the same level as you might expect from a decent sysadmin. A good programmer with an active interest in learning languages could be expected to learn that much Perl in very short order.
Of course the level of programming skill that this feat implies is another story. For instance it is well beyond what I'd expect from a random Perl hacker in that time frame. For one thing Perl 5 had only been out for a year, people hadn't had enough time to master OO based on experience with Perl. Matz, of course, already had 15 years of OO experience...
Of course you might ask why he'd pick Perl to imitate if it wasn't a language that he was a particular expert in. The answer is simple, he wanted to write a scripting language. In 1995 Perl was clearly the best of breed scripting language out there. Perl had no serious challenger to that title. Likewise Smalltalk was the best of breed OO language. So those are what Matz used as templates for his OO scripting language, even though he was primarily a Lisp hacker.