Unless I've made a typo, the following two snippets should be equivalent:

my $last = -50; # set to -50 so that the first coordinate will be incl
+uded as long as it is 1 or more
map {say if $_ > $last + 50; $last = $_} @n;
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my $last = -50;
for (@n) {
    if ($_ > $last + 50) {
        say $_;
    }
    $last = $_;
}
[download]