You will be able to access the main program's %hash1 variable directly from a package if it is not declared with my (whose visibility would be limited to the block (or file if it's not in an explict block) that it is declared in). You will need to explictly specify the package of the variable with like %::hash1 or %main::hash1 (and, if you are using strict as you should be, you must decalre %hash1 in the main program with our or use vars.)

However, this is probably not good design. It would probably be best if you made your module not be dependent on what variables the main program is using. That is, you would instead pass the relevant hash to the module's functions (ideally as a reference.)

update: changed references link.