This:

 (my ($x, $y, $z) = qw( 1 2 3 )) = qw( a b c );
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Is semantically equivalent to this,

 my ($x, $y, $z) = qw( 1 2 3 ); # $x = '1', $y = '2', $z = '3'.
 ($x, $y, $z)    = qw( a b c ); # $x = 'a', $y = 'b', $z = 'c'.
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