@ ProgramNode (location: (1,0)-(1,14))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,14))
    └── body: (length: 1)
        └── @ InterpolatedStringNode (location: (1,0)-(1,14))
            ├── flags: ∅
            ├── opening_loc: (1,0)-(1,1) = "\""
            ├── parts: (length: 5)
            │   ├── @ EmbeddedVariableNode (location: (1,1)-(1,4))
            │   │   ├── operator_loc: (1,1)-(1,2) = "#"
            │   │   └── variable:
            │   │       @ InstanceVariableReadNode (location: (1,2)-(1,4))
            │   │       └── name: :@a
            │   ├── @ StringNode (location: (1,4)-(1,5))
            │   │   ├── flags: frozen
            │   │   ├── opening_loc: ∅
            │   │   ├── content_loc: (1,4)-(1,5) = " "
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: " "
            │   ├── @ EmbeddedVariableNode (location: (1,5)-(1,9))
            │   │   ├── operator_loc: (1,5)-(1,6) = "#"
            │   │   └── variable:
            │   │       @ ClassVariableReadNode (location: (1,6)-(1,9))
            │   │       └── name: :@@a
            │   ├── @ StringNode (location: (1,9)-(1,10))
            │   │   ├── flags: frozen
            │   │   ├── opening_loc: ∅
            │   │   ├── content_loc: (1,9)-(1,10) = " "
            │   │   ├── closing_loc: ∅
            │   │   └── unescaped: " "
            │   └── @ EmbeddedVariableNode (location: (1,10)-(1,13))
            │       ├── operator_loc: (1,10)-(1,11) = "#"
            │       └── variable:
            │           @ GlobalVariableReadNode (location: (1,11)-(1,13))
            │           └── name: :$a
            └── closing_loc: (1,13)-(1,14) = "\""