Item 23: Understand the difference between my and local .
Item 24: Avoid using @_ directlyunless you have to.
Item 25: Use wantarray to write subroutines returning lists.
Item 26: Pass references instead of copies.
Item 27: Use hashes to pass named parameters.
Item 28: Use prototypes to get special argument parsing.
Item 29: Use subroutines to create other subroutines.