snakeyaml-oct-int

irb(main):002:0> Dir['classpath/*'].each {|jar| require File.expand_path(jar) }
=> ["classpath/annotations-3.0.0.jar", "classpath/aopalliance-1.0.jar", "classpath/bval-core-0.5.jar", "classpath/bval-jsr303-0.5.jar", "classpath/commons-beanutils-core-1.8.3.jar", "classpath/commons-lang3-3.1.jar", "classpath/embulk-core-0.7.10.jar", "classpath/embulk-standards-0.7.10.jar", "classpath/guava-18.0.jar", "classpath/guice-4.0.jar", "classpath/guice-multibindings-4.0.jar", "classpath/icu4j-54.1.1.jar", "classpath/jackson-annotations-2.5.3.jar", "classpath/jackson-core-2.5.3.jar", "classpath/jackson-databind-2.5.3.jar", "classpath/jackson-datatype-guava-2.5.3.jar", "classpath/jackson-datatype-joda-2.5.3.jar", "classpath/jackson-module-guice-2.5.3.jar", "classpath/jansi-1.11.jar", "classpath/javax.inject-1.jar", "classpath/joda-time-2.8.1.jar", "classpath/jruby-complete-9.0.4.0.jar", "classpath/logback-classic-1.1.3.jar", "classpath/logback-core-1.1.3.jar", "classpath/msgpack-core-0.8.1.jar", "classpath/netty-buffer-5.0.0.Alpha1.jar", "classpath/netty-common-5.0.0.Alpha1.jar", "classpath/slf4j-api-1.7.12.jar", "classpath/slice-0.9.jar", "classpath/snakeyaml-1.14.jar", "classpath/validation-api-1.1.0.Final.jar"]
irb(main):003:0> org.yaml.snakeyaml.Yaml.new.load("argument: 010391")
=> {"argument"=>10391.0}
irb(main):004:0> org.yaml.snakeyaml.Yaml.new.load("argument: 0103")
=> {"argument"=>67}
irb(main):005:0> org.yaml.snakeyaml.Yaml.new.load("argument: 01a")
=> {"argument"=>"01a"}

snakeyaml-1.14.jar and jruby 9.0.0.0.