perl -e "print eval qq/require DBI; DBI::SQL_VARCHAR/ || $@;"
>>> prints 'DBI::SQL_VARCHAR'

perl -e "print eval qq/require DBI; DBI::SQL_XVARCHAR/ || $@;"
>>> prints 'DBI::SQL_XVARCHAR'

perl -e "print eval qq/require DBI; DBI::SQL_VARCHAR()/ || $@;"
>>> prints '12'

perl -e "print eval qq/require DBI; DBI::SQL_XVARCHAR()/ || $@;"
>>> prints 'Can't locate auto/DBI/SQL_XVARCHA.al...'

perl -e "$it=q/SQL_VARCHAR/; print eval qq/require DBI; DBI::$it/ || $@;"
>>> prints 'DBI::SQL_VARCHAR'

perl -e "$it=q/SQL_VARCHAR/; print eval qq/require DBI; DBI::$it()/ || $@;"
>>> prints '12'

perl -e "$it=q/SQL_XVARCHAR/; print eval qq/require DBI; DBI::$it/ || $@;"
>>> prints 'DBI::SQL_XVARCHAR'

perl -e "$it=q/SQL_XVARCHAR/; print eval qq/require DBI; DBI::$it()/ || $@;"
>>> prints 'Can't locate auto/DBI/SQL_XVARCHA.al...'

##</code><code>##

   eval "DBI::SQL_VARCHAR";
   # is the same as 
   $it='DBI::SQL_VARCHAR'; eval { $it };