#!/usr/bin/env perl
+
+
use strict;
+
use warnings;
+
use List::Util qw(sum);
+
+
# For each $n, convert $n to hex digits, add the digits together. If t
+he
# result has more than one hex digit, repeat this process adding the
+
# digits together. When there is only one hex digit remaining, if the
+
# digit is a '5', an 'a', or an 'f', the original number was divisible
+
# by 5.
+
+
for my $n (1..100) {
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my $h = sprintf '%x', $n;
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while(length($h) > 1) {
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$h = sprintf '%x', sum(map {hex $_} split //, $h);
}
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print "$n is a multiple of 5\n" if $h =~ m/^[5af]$/;
+
}
Output:
5 is a multiple of 5
10 is a multiple of 5
15 is a multiple of 5
20 is a multiple of 5
25 is a multiple of 5
30 is a multiple of 5
35 is a multiple of 5
40 is a multiple of 5
45 is a multiple of 5
50 is a multiple of 5
55 is a multiple of 5
60 is a multiple of 5
65 is a multiple of 5
70 is a multiple of 5
75 is a multiple of 5
80 is a multiple of 5
85 is a multiple of 5
90 is a multiple of 5
95 is a multiple of 5
100 is a multiple of 5
