But without polluting the namespace with the dummy name $o, cause the scope is limited.

Not that weird, it returns a lexical scalar variable for the slot. But without polluting the namespace with the dummy name $o, cause the scope is limited.

Sure its weird to write  do { my $o} when it could write undef or "DUMMY" or "fix" or "V: $VAR1->{a}" or any other string

> when it could write ... "V: $VAR1->{a}"

MidLifeXis already explained purity

> when it could write undef or "DUMMY" or "fix"

see Scalar::Util readonly to understand the difference between passed literals and variables.

readonly SCALAR
           Returns true if SCALAR is readonly.

               sub foo { readonly($_[0]) }

               $readonly = foo($bar);              # false
               $readonly = foo(0);                 # true
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If you think Data::Dumper should be cleverer instead of playing safe, you are free to provide a patch.

> Sure its weird

Claiming a "bug" without deeper knowledge seems weird to me.

Cheers Rolf

_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}