The qw// operator is discussed in perlop. The semantics are essentially that within a qw quote-like operator, whitespace separates elements. So: qw{ABCGE ABCGE} represents two elements, not one. This is different behavior from q// or qq//, which would return a single element:

my @list = qw{ABCDE DEFGH}; # @list has two elements.
my @list = qq{ABCDE DEFGH}; # @list has one element.
my @list = q{ABCDE DEFGH};  # @list has one element.
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Therefore, these two things ARE equivalent:

my @list = qw{ABCDE DEFGH};      # Two elements.
my @list = ('ABCDE', 'DEFGH');   # Two elements.
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And these are equivalent:

my @list = ([qw{ABCDE DEFGH}], [qw{IJKLM NOPQR}]);  # Two array-refs w
+ith two elements in each.
my @list = (['ABCDE, 'DEFGH'], ['IJKLM', 'NOPQR']); # Two array-refs w
+ith two elements in each.
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And the following produces four elements:

my @list = ('ABCDE', qw{DEFGH IJKLM}, 'NOPQR');  # Four elements.