A my variable can't be used outside of the block (the enclosing braces) in which it's declared. When a subroutine returns a value (or values), there has to be another variable to take up those values. In other words, your return @db needs the function call to be my @db = get_all_records()

Note that the @db inside the function is completely different to the @db outside the function. It just happens to have the same name.

dominus wrote a classic tutorial on this subject. See Coping with Scoping.