That's not a problem, and generally speaking, you don't need any CPAN module to support unicode, as Perl core supports it.

Obviously you need to learn more about unicode, and you can always come back with more specific questions. Luckily you don't need to learn anything about Japanese, as what you care is the encoding, not the language itself. From your point of view, a web page in Japanese, is just a stream of charactrers (numbers), in this sense, there is no difference between Japanese and English. Of course, the persons who provide and design the content need to know Japanese, but that's a different story.

However, the way to enter Japanese characters and display them on screen is handled by the entry tool, browser, and OS, which are not part of Perl. Japanese characters are either entered thru special keyboard, or nowadays mostly thru special 'code' by using abc123's on an English keyboard. This 'code' is not the unicode we are talking about, but rather the code for each character to allow entering (typing).

Display is not a problem, as most of the browsers support most of the main languages by default or by using plug-ins. Down to the bottom, displaying is just to translate a stream of predefined code into a stream of predefined pictures (group of pixels). Entering is either supported by OS, or by using free-dowloaded or paid tools (lots of tools support both Chinese and Japanese at the same time, as Japanese usese lots of Chinese characters), but that is what the user should be worry about not you. Don't worry, as those people read Japanese web pages, send email in Japanese ... have their own system set up already, as this is not the first time people see a page in Japanese in cyber world.