Doh!

The following code may be of interest:

use strict;
use warnings;

my @pnt_x_values = (-12, 0, 23);
my @pnt_y_values = (-83, 34, -76);

my @poly_x_min = (-13, 45, 22);
my @poly_x_max = (-11, 49, 24);
my @poly_y_min = (-82, 33, -2);
my @poly_y_max = (-84, 35, -6);

for my $polyI (0 .. $#poly_x_min) {
    my $x1 = $poly_x_min[$polyI];
    my $x2 = $poly_x_max[$polyI];
    my $y1 = $poly_y_min[$polyI];
    my $y2 = $poly_y_max[$polyI];
    my @poly = map {{x => $_->[0], y =>$_->[1]}}
        ([$x1, $y1], [$x2, $y1], [$x2, $y2], [$x1, $y2]);

    for my $pi (0 .. $#pnt_x_values) {
        my %point = (x => $pnt_x_values[$pi], y => $pnt_y_values[$pi])
+;

        next unless PointInPoly (\%point, \@poly);
        print 'Point ' . ($pi + 1) . ' inside poly ' . (1 + $polyI) . 
+"\n";
    }
}


sub PointInPoly {
    my ($point, $poly) = @_;
    my $wCount = 0;

    for my $i (0 .. $#$poly - 1, -1) {
        # edge from$poly->[$i] to$poly->[$i + 1]
        if ($poly->[$i]{y} <= $point->{y}) {
            # start y <= $P->{y}
            if ($poly->[$i + 1]->{y} > $point->{y}) {
                # an upward crossing
                if (isLeft ($poly->[$i], $poly->[$i + 1], $point) > 0)
+ {
                    # $P left of edge
                    ++$wCount;    # have a valid up intersect
                }
            }
        } else {
            # start y > $P->{y} (no test needed)
            if ($poly->[$i + 1]->{y} <= $point->{y}) {
                # a downward crossing
                if (isLeft ($poly->[$i], $poly->[$i + 1], $point) < 0)
+ {
                    # $P right of edge
                    --$wCount;    # have a valid down intersect
                }
            }
        }
    }
    return $wCount;
}


sub isLeft {
    my ($P0, $P1, $P2) = @_;

    return ($P1->{x} - $P0->{x}) * ($P2->{y} - $P0->{y})
            - ($P2->{x} - $P0->{x}) * ($P1->{y} - $P0->{y});
}
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Prints:

Point 1 inside poly 1
[download]