The return value from an empty list when used in a scalar context is undef.

so why should the condition succeed?

 perl -e '$empty = (); print ("hi there\n") if \!$empty;
__END__
hi there
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perl -e '$empty = (); print ("hi there\n") if \!defined($empty);'
__END__
hi there
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PS: I am using \! to avoid my csh from interepreting it as a special shell character.