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diff --git a/2023/21.pl b/2023/21.pl
new file mode 100755
index 0000000..bfc568a
--- /dev/null
+++ b/2023/21.pl
@@ -0,0 +1,36 @@
+#!/usr/bin/perl -w
+
+use v5.38;
+
+my @gxys;
+my $y = 0;
+while (<>) {
+	while (/#/g) {
+		my $x = pos()-1;
+		push @gxys, [ $x, $y ];
+	}
+	$y++;
+}
+
+my %x_gxy = map { $_->[0] => 1 } @gxys;
+my %y_gxy = map { $_->[1] => 1 } @gxys;
+
+my $steps;
+for my $i (0 .. $#gxys-1) {
+	for my $j ($i .. $#gxys) {
+		my ($x1, $y1) = $gxys[$i]->@*;
+		my ($x2, $y2) = $gxys[$j]->@*;
+
+		($x1, $x2) = ($x2, $x1) if $x1 > $x2;
+		for ($x1+1 .. $x2) {
+			$steps += $x_gxy{$_} ? 1 : 2;
+		}
+
+		($y1, $y2) = ($y2, $y1) if $y1 > $y2;
+		for ($y1+1 .. $y2) {
+			$steps += $y_gxy{$_} ? 1 : 2;
+		}
+	}
+}
+
+say $steps;