Pass by reference is preferred over pass by value when making a call to a subroutine, because at the lowest level it means a data pointer is passed on the call stack, rather than a copy of the contents of that data pointer.

This makes a difference because it takes time and space to copy data from a local location to a stack before the call, and more time and space to copy data from the stack to another local location. You can save time and space at both ends by just using a pointer, at the slight cost of additional complexity.

The complexity is well-hidden in Perl (and other high level languages); we just add a single character to indicate the indirection in the subroutine call, and understand that we'll be dealing with a reference in the subroutine.

Once you are more experienced in writing code, this will come very easily to you.

Alex / talexb / Toronto

"Groklaw is the open-source mentality applied to legal research" ~ Linus Torvalds

In reply to Re: Array or Hash Reference to Subroutine by talexb
in thread How to use @EXPORT by pkperl

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