perl generally does no displaying , it leaves that up to the shell/GUI toolkit/browser ... so you'll have to rephrase your question, provide more detail

See perlunitut: Unicode in Perl

Maybe your terminal doesn't understand UTF-8. Or you have one more decoding step than encoding steps. Or there's something wrong with line 42 of your program. How can I know, without seeing your code? Medidate on it.

See also: Character Encodings in Perl.

Redirect it's output to file and see that file with your browser(Firefox or something). You can know wheter it is really troubled string or it is a problem of application that you are using( terminal, excel .. and so on).

Documents for encoding ... they are not so long documents.

perlunitut	6 pages	Very very short overview for unicode in perl + FAQ.
The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)	8 pages	About Charcter Set, Code Page, Unicode itself. Short History of Unicode.
perluniintro	12 pages	This is the first thing to read (I think).
Character Encodings in Perl	7 pages	all-in-one doc for encoding. Written by German Author.
perlunicode	20 pages	Main document of perl's unicode. Through and precise, or too much for beginner.
Perl Programming/Unicode UTF-8	15 pages	This document explains internal encoding of Perl (N8CS, utf-8) and also describe other problems. When you stumbled with 0x80-0xFF problem, this document explains the reason.