* Michael Carmen rewrote this answer to clarify some of the memory management issues. I usually don't pay attention to this level of Perl and I'm not an OS guru, so an internals-type person may want to verify the change.
Index: perlfaq3.pod =================================================================== RCS file: /cvs/public/perlfaq/perlfaq3.pod,v retrieving revision 1.44 diff -u -d -r1.44 perlfaq3.pod --- perlfaq3.pod 21 Jan 2005 12:08:04 -0000 1.44 +++ perlfaq3.pod 26 Jan 2005 20:06:53 -0000 @@ -649,23 +649,25 @@ =head2 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. +(contributed by Michael Carman) + +You usually can't. Memory allocated to lexicals (i.e. my() variables) +cannot be reclaimed or reused even if they go out of scope. It is +reserved in case the variables come back into scope. Memory allocated +to global variables can be reused (within your program) by using +undef()ing and/or delete(). + +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. +or should be worrying about much in Perl. + +See also "How can I make my Perl program take less memory?" =head2 How can I make my CGI script more efficient? -- brian d foy, [EMAIL PROTECTED]
