Common JSP EL examples

Here are a few commonly used JSP EL examples that you can use in your Correspondence Management solution:

To add two numbers:
```
${number1 + number2}
```
To concatenate two strings:
```
${str1} ${str2}
```
To compare two numbers:
```
${age < 18}
```

You can find more information in the JSP EL specification. The client-side expression manager does not support certain variables and functions in the JSP EL specification, specifically:

Collection indexes and map keys (using the [] notation) are not supported in variable names for expressions evaluated on the client-side.
Complex types are currently not supported as parameter types or return types of functions used in expressions. The only allowed types are:
- java.lang.String
- java.lang.Character
- char
- java.lang.Boolean
- boolean
- java.lang.Integer
- int
- java.lang.Short
- short
- java.lang.Byte
- byte
- java.lang.Double
- double
- java.lang.Long
- long
- java.lang.Float
- float
- java.util.Calendar
- java.util.Date