$ perl -e 'print substr("a\x{2322}bcd", 0, 3), "\n";' | hexdump
00000000  61 e2 8c a2 62 0a

##</code><code>##

$ perl -e 'print "a\x{2322}bcd\n"' > uni-file
$ perl -ne 'print substr($_,0,3), "\n"' uni-file | hexdump
00000000  61 e2 8c 0a

##</code><code>##

$ perl -ne 'utf8::upgrade($_);
> print substr($_,0,3), "\n"' uni-file |
> hexdump
00000000  61 e2 8c 0a

##</code><code>##

$ perl -ne 'BEGIN{binmode(STDIN,":utf8");
> print substr($_,0,3), "\n"' uni-file |
> hexdump
00000000  61 e2 8c a2 62 0a

##</code><code>##

$io->open($in_file, "<:raw:encoding(cp1252)")  ||  die(...);

##</code><code>##

while (!$io->eof) {
   $cols = $csvin->getline($io);
   ...
   $str = $col[0];
   print substr($str,0,3), "\n";   # XXX cuts through utf8 multibyte!
}