Your calculation results in a floating-point numeric result which you are comparing to an integer. Change:

    my $adjusted_hue = $hues[$index] + ($scaled_index - $index)*($hues
+[$index + 1] - $hues[$index]);
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to:

    my $adjusted_hue = sprintf '%d', $hues[$index] + ($scaled_index - 
+$index)*($hues[$index + 1] - $hues[$index]);
[download]

• FAQ: Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)?
• sprintf