Given that with the "sqlldr" method you would have to delete the "bad" data after it was discovered to be bad, it seems like you'd be wasting all that effort. Using Perl to validate the data before you load it from the flat file would be trivially easy and would avoid the wasted "round trips".

# Checks comma-separated elements
perl -F, -wane'for (@F){die "Improper data\n" if length($_)>255}' file
+name.txt
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