I agree there are some edge cases to consider depending on the use-case... and I don't know the OPs use cases good enough.

But because of cleaner scope and loop-control statements I'd rather prefer

for (my $iter = get_iter(); my ( $widget ) = $iter->(); ) {
   ...
}
[download]

over

my $iter = get_iter();

while ( my ( $widget ) = $iter->() ) {
   ...
}
[download]

This approach will put $iter in a tight scope and properly destroy.

Needless to say, if Perl had macros like Lisp, we wouldn't need to repeat that discussion again and again...

Keyword-simple could solve this, but is restricted to statements only.

see also

Can I check if a loop's scope is entered for the first time?