Returns true if the reference is blessed into package type or inherits from that package. Can be called as a static or object method call, or as a subroutine:
Returns true if the first argument is a reference and either of the following is true:UNIVERSAL::isa(val, type)
val is a blessed reference and is blessed into package
or inherits from package
val is a reference to a
type of Perl variable (e.g., '