If you set up your form properly:

<form accept-charset="utf-8">
[download]

the chractes you submit will be sent to the web server in unicode, not in the alternate encoding scheme you describe. It will also help if you put the document itself into UTF-8 as-well by setting the content-type (either in the HTTP header or in a meta-tag) to charset=utf-8.

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update

Here are the links I promised:

• i18n: HTML Character set issues beyond HTML3.2 (be sure to see his FORM page)
• HTML Unleashed: Internationalizing HTML this is the whole chapter from teh book online, not a link to buy the book.
• World-Wide Character Sets, Languages, and Writing Systems from w3c
• Unicode.org homepage of the unicode consotrtium

In addition to the unicode conversion modules mentioned above (Unicode::Map, Unicode::Map8, cpan::Unicode::MapUTF8) you may also want to check out the Text::Iconv module which also provides character set conversion functionality.