It doesn't, with rare exceptions.
[Details.]
TCT takes memory leaks [ref] very seriously. Few ever escape into a release, and few known ones survive long.
However, there are at least an order of magnitude more perceived memory leaks. These result mainly from two causes:
[More explanation.]
[Pertinent post2 [L1 ] [L2 ] by tclguy on Tcl's allocator, high-water marking, ...]
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