However, 
if ( $a{'abd'} and $a{'abd'}->[0])
   { print "yes\n"}

[download]
is the same.

Not really. Array element maybe defined but false. You can't omit defined as easy as exists.

In reply to Re^4: restricting values to a nested datastructure by zwon
in thread restricting values to a nested datastructure by babp

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