Closures that enclose themself represent a reference cycle which is a.k.a. a memory leak. If you need a self referencing sub you should localize a glob to do it. Ie:

local *recursive=sub { ... recursive(...); };
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This keeps the self references "soft" and means that when it goes out of scope the sub will be freed. Doing it via lexicals is not correct

my $recursive;
$recursive=sub{ ... $recursive->(...); };
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as it will leak. (Meaning the sub referenced by $recursive will not be freed until global destruction.)

See also Sub::Recursive which handles all that for you in a clean way.

use Sub::Recursive;

my $recursive = recursive { ... $REC->(...) ... };
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