Current object placeholder only works when its on the right side of an logical expression

The following code works as expected
```
require 'jsonpath'

json = <<-JSON
{
"colors": [
"yellow",
"green"
]
}
JSON

path = JsonPath.new("$.colors[?(@ == 'green')]")
path.on(json)

```

but when we do this for the same json as in the above example, the filtering is not working as expected

```
path = JsonPath.new("$.colors[?('green' == @)]")
path.on(json)

```