Abstract AS2

// {
//   action: "constant-pool",
//   pool: []
// }

@setConstantPool();

// {
//   action: "constant-pool",
//   pool: ["foo"]
// }

@setConstantPool("foo");

// {
//   action: "constant-pool",
//   pool: ["foo", "bar"]
// }

@setConstantPool("foo", "bar");

Adobe documentation

ActionConstantPool creates a new constant pool, and replaces the old constant pool if one already exists.

Field	Type	Comment
ActionConstantPool	ACTIONRECORDHEADER	ActionCode = 0x88
Count	UI16	Number of constants to follow
ConstantPool	STRING[Count]	String constants