Adding, replacing or removing elements an array over which you are iterating should be avoided.

for (@a) {
   push @a, ...;    # XXX Avoid
   splice @a, ...;  # XXX Avoid
   pop @a;          # XXX Avoid
}
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Changing the value of an array element is fine, as is changing variables referenced by them

for my $person (@people) {
   # Do anything you want to $person
   # Do anything you want to $person->{whatever}
}
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In your code, you are iterating over a list of numbers that you can't even change if you wanted to. There's definitely no harm in that.