You appear to be attempting to assign to a scalar from a hash key (also a scalar) 
Instead of:
 my $x_axis_label = %specifications{'Central_comparisons'}{'Primary'};

Try:
 my $x_axis_label = $specifications{'Central_comparisons'}{'Primary'};

[download]
same for the second line.

In reply to Re^2: Global symbol requires explicit package name by djshultz
in thread Global symbol requires explicit package name by Win

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