@ ProgramNode (location: (1,0)-(6,9))
├── flags: ∅
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(6,9))
    ├── flags: ∅
    └── body: (length: 2)
        ├── @ StringNode (location: (1,0)-(1,8))
        │   ├── flags: newline
        │   ├── opening_loc: (1,0)-(1,8) = "<<' FOO'"
        │   ├── content_loc: (2,0)-(3,0) = "[Bug #19539]\n"
        │   ├── closing_loc: (3,0)-(4,0) = " FOO\n"
        │   └── unescaped: "[Bug #19539]\n"
        └── @ StringNode (location: (6,0)-(6,9))
            ├── flags: newline
            ├── opening_loc: (6,0)-(6,9) = "<<-' FOO'"
            ├── content_loc: (7,0)-(8,0) = "[Bug #19539]\n"
            ├── closing_loc: (8,0)-(9,0) = " FOO\n"
            └── unescaped: "[Bug #19539]\n"
