You can reduce the number of comparisons by recognising that your ranges are a cover of the total range, and disjoint. That lets you check against just one of the bounds of each subrange. For example, in japhy's solution, the loop over @settings can be rewritten,

    for (@settings) {
        if ($boo < $_->[1]) {
            ($scalar, $msg) = @{$_}[2,3];
            last;
        }
    }
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The savings are not always as great as they appear. A similar effect can be obtained by testing the upper bound first in the redundant form. The short-circuiting and operator will take care of the savings.

'Windowing' or 'binning' operations like this can be done with a logarithmic number of comparisons, using a binary tree to store the limits. The added complexity of the code to support that is probably not justified in so small a set of bins as this.

After Compline,
Zaxo