IO::Handle appears to allow access to setbuf() and setvbuf(). From the perldoc:

If the C functions setbuf() and/or setvbuf() are available, then "IO::Handle::setbuf" and "IO::Handle::setvbuf" set the buffering policy for an IO::Handle. The calling sequences for the Perl functions are the same as their C counterparts--including the constants "_IOFBF", "_IOLBF", and "_IONBF" for setvbuf()--except that the buffer parameter specifies a scalar variable to use as a buffer. You should only change the buffer before any I/O, or immediately after calling flush.

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print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
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