undef @x;

use Data::Dumper;
print Dumper(\@x);

!defined(@x) && print "not defined\n";

[download]

Unfortunately, Data::Dumper shows \@x == []

which means that @x is an array named for an empty list, not that @x is undefined.

The difference cropped up for me when getting back data from grep, which returns undef when nothing in the input list matches the criteria of the code block.

In reply to What Data::Dumper dumps is not necessarily what is there by princepawn

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