How do you find out if the code you write is shared between processes or not? The code should remain shared, except when it is on a memory page used by variables that change. As you know, a variable becomes unshared when a process modifies its value, and so does the memory page it resides on, because the memory is shared in memory-page units.

Sometimes you have variables that use a lot of memory, and you consider their usage read-only and expect them to be shared between processes. However, certain operations that seemingly don't modify the variable values do modify things internally, causing the memory to become unshared.

Imagine that you have a 10 MB in-memory database that resides in a single variable, and you perform various operations on it and want to make sure that the variable is still shared. For example, if you do some regular expression (regex)-matching processing on this variable and you want to use the pos( ) function, will it make the variable unshared or not? If you access the variable once as a numerical value and once as a string value, will the variable become unshared?

The Apache::Peek module comes to the rescue.