What variable lifecycle problem did you see? I looked 3 times and didn't find any.

Look very carefully at the lifecycle(s) of $field. If you don't see the problem, consider this:

  $foo = 1;
  if ( 1 ) {
      my $foo = 2;
  }
  print "$foo\n";
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Looking at this, what would you expect it to print?

I doubt this has anything to do with the problem you originally reported, but it is one more red flag among many raised by the code fragment you posted.