that's how the term is defined in the perldocs:

dynamic scoping

Dynamic scoping works over a dynamic scope, making variables visible throughout the rest of the block in which they are first used and in any subroutines that are called by the rest of the block. Dynamically scoped variables can have their values temporarily changed (and implicitly restored later) by a local operator. (Compare lexical scoping.) Used more loosely to mean how a subroutine that is in the middle of calling another subroutine "contains" that subroutine at run time.