I'm not qualified to say that it's wrong. I will say that it doesn't seem like the right tool. Just for an example, consider the hazard of accidentally doing something like:

my @b = grep { s/apples/oranges/ } @a;
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If what you meant was to have a @b basket of oranges, and an  @a basket of apples, you'll be quite unhappy to find that grep has eaten all of your apples.

mkmcconn