The my keyword declares variables. You have to declare a variable before you use it (under use strict), otherwise you'll get the Global symbol "$VERBOSE" requires explicit package name at .. type of message. But you can't re-declare a variable, otherwise you'll get the "my" variable $DEBUG masks earlier declaration in same scope .. type of message.

Define a variable just once, and before it's needed, then Perl won't (or shouldn't) complain.