The <<= and >>= operators (http://www.postgresql.org/docs/9.1/static/functions-net.html#CIDR-INET-OPERATORS-TABLE) are missing in sequel/lib/sequel/sql.rb so it is not possible to use the operators in Sequel expressions (Sequel::Error: Invalid operator <<=).
Sequel::Error: Invalid operator <<=
Those operators don't exist in ruby (well, they exist, but a <<= b is basically a = a << b, you can't define <<= separately).
a <<= b
a = a << b
If you want to use these operators, you should use literal SQL: Sequel.lit("? <<= ?", :a, :b)
Sequel.lit("? <<= ?", :a, :b)