The ASCII question mark is typically what you get when something tries to convert some unicode character into some non-unicode character set that does not contain the character in question.

For example, the following script will produce "foo??", because the string literal has unicode Cyrillic for the fourth and fifth characters, but perl is being told to convert it to iso-8859-1 (Latin-1), which does not contain any Cyrillic characters -- that is, the unicode code points for Cyrillic cannot be mapped into the single-byte character codes for Latin-1, so the conversion produces "?" instead. 

perl -MEncode -le '$_=encode("iso-8859-1","foo\x{041d}\x{0418}"); prin
+t'

[download]
It's not just perl that does this. Anything/everything that supports conversion between unicode and other encodings will behave the same way when faced with the same inappropriate task.

To figure out where the question marks are coming from, figure out the last point where the data were in unicode, and what sort of bad assumption is being made at that point to convert the encoding to something else.

In reply to Re^7: Character encoding of microns by graff
in thread Character encoding of microns by joec_

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.