Thanks for that. Have understood autovivification of variables when in assignment, increment, etc. but not realized it could affect a test. Googling on autovivification, I found in 'Perl Maven' blog, https://perlmaven.com/autovivification an example, with

"This is quite unfortunate. This means we have changed the state of the %people has just by observing it. ... I think these undesirable cases are now generally considered to be a bug in Perl. Unfortunately it is very unlikely that this bug will be fixed in Perl 5 as there is a lot of code out in the wild (both on CPAN and in companies) that rely on this behavior. Correcting the behavior would break a lot of code."

In the event, I am now wiser. Unfortunately, when creating some sparse hashs of arrays I do rely upon autovivification, with tests to identify their non-existence when necessary. But will now know how to adapt ...

In reply to Re^2: Defined test creates non-empty hash value by glendeni
in thread Defined test creates non-empty hash value by glendeni

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