The down side is that last becomes equivalent to next (unless you use a label).

$ perl -le'for (1..2) { { print; last; } cleanup; }'
1
2
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The up side is that it solves the following problem nicely:

$ perl -Mstrict -e'for (@ARGV) { my $x; } continue { cleanup($x) }'
Global symbol "$x" requires explicit package name at -e line 1.
-e had compilation errors.
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