Others have explained how to get the results you want.

For the benefit of potentilal newbies, here is a clarification on what went wrong with the original code :

my @masterarray = qw(@array1 @array2 @array3);
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It did NOT DWIM !

As you have discovered, that code is equivalent to :

my @masterarray = ('@array1','@array2','@array3');
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and this is clear in examples the documentation for qw (perldoc perlfunc).

Although it is not explicit in the documentation, the qw operator DOES NOT INTRAPOLATE.