How do you know the reference of a variable whether it is a reference,scaller, hash or array?

Answer : There is a 'ref' function .

Perl provides the ref() function so that you can check the reference type before dereferencing a reference

The ref() function can return are:

Function Call	Return Value
ref( 10 );	undefined
ref( \10);	SCALAR
ref( \{1 => ; "Joe"} );	HASH
ref(\&firstSub );	CODE
ref( \\10);	REF