FAQ 3.19: How can I free an array or hash so my program shrinks?

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3.19: How can I free an array or hash so my program shrinks?

    You usually can't. On most operating systems, memory allocated to a
    program can never be returned to the system. That's why long-running
    programs sometimes re-exec themselves. Some operating systems (notably,
    systems that use mmap(2) for allocating large chunks of memory) can
    reclaim memory that is no longer used, but on such systems, perl must be
    configured and compiled to use the OS's malloc, not perl's.

    However, judicious use of my() on your variables will help make sure
    that they go out of scope so that Perl can free up that space for use in
    other parts of your program. A global variable, of course, never goes
    out of scope, so you can't get its space automatically reclaimed,
    although undef()ing and/or delete()ing it will achieve the same effect.
    In general, memory allocation and de-allocation isn't something you can
    or should be worrying about much in Perl, but even this capability
    (preallocation of data types) is in the works.


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