First, a potential warning: Most database interfaces have a max size for the the SQL statement to be processed. You might run into that with the first query eventually. Look and see if Win32::ODBC supports the concept of Bind variables.
Or check out DBD::ODBC, which would making future porting easier.

Second, the issue likely is not the whether the column can support the data, because I think the 'text' column type can support up to 2 GB (IIRC). The issue is more likely to be in the database driver. Have you went in with another tool to see if the data was added, and whether that tool can pull it up? If it can, you will have to read the Win32::ODBC documentation. Here is a peice of it(from the ActivePerl 5.6 port):

And what are the benefits of this module?

• The number of ODBC connections is limited by memory and ODBC itself (have as many as you want!).
• The working limit for the size of a field is 10,240 bytes, but you can increase that limit (if needed) to a max of 2,147,483,647 bytes. (You can always recompile to increase the max limit.)
• You can open a connection by either specifing a DSN or a connection string!
• You can open and close the connections in any order!
• Other things that I can not think of right now... :)

In particular this piece seems relevant:

SetMaxBufSize ( SIZE )
This sets the MaxBufSize for a particular connection. This will most likely never be needed but...
The amount of memory that is allocated to retrieve the field data of a record is dynamic and changes when it need to be larger. I found that a memo field in an MS Access database ended up requesting 4 Gig of space. This was a bit much so there is an imposed limit (2,147,483,647 bytes) that can be allocated for data retrieval.
Since it is possible that someone has a database with field data greater than 10,240, you can use this function to increase the limit up to a ceiling of 2,147,483,647 (recompile if you need more).
Returns the max number of bytes.

Hope this helps.