What I meant by look at your NLS settings is that OCI needs to know the encoding of the strings passed to it. If you say the strings are iso8859 they will be interpreted as is8859 and if you say they are utf8 they will be interpreted as utf8 - you have to have one or the other.

By adding char(1024) you turned the string into unicode and so DBD::Oracle will pass utf8 strings as DBD::Oracle DOES know the string you passed it is unicode but then the NLS setting comes in to play since OCI will use that to decide the encoding of the client character-set.

If you want to use iso8859 then make sure you NLS setting is correct and don't use unicode strings. If you want to use unicode strings then set your NLS setting to utf8 and change the iso8859 strings to unicode. Don't try and mix them without performing the conversion.