As you can find in perlsyn, post-position modifiers are only possible with "simple statements". Block or a statement with a modifier are not simple statements.

To turn a block into a simple statement, wrap it in a do:

do { statement1; statement2 } for @array;
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But I'm not sure it still buys you anything.

Also, note that  do { ... } while (condition) checks the condition after the first iteration of the loop.