Whenever you're suspecting memory leaks, it's very helpful to mention what version of perl that you're using. Also make sure that you're using use strict.

You haven't lexically scoped $ts, not that that'd cause bloat this bad. Also a minor style nit. Since you've already declared %plaq lexically you clould just push a reference to it rather than rebuilding a new hashref just to push.

...
push @plaque, \%plaq;
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