1 files changed, 26 insertions, 0 deletions
diff --git a/challenge-082/polettix/perl/ch-2.pl b/challenge-082/polettix/perl/ch-2.pl
new file mode 100644
index 0000000000..62e1b7ad38
--- /dev/null
+++ b/challenge-082/polettix/perl/ch-2.pl
@@ -0,0 +1,26 @@
+#!/usr/bin/env perl
+use 5.024;
+use warnings;
+use English qw< -no_match_vars >;
+use experimental qw< postderef signatures >;
+no warnings qw< experimental::postderef experimental::signatures >;
+
+sub is_interleaving ($A, $B, $C) {
+   my ($lA, $lB, $lC) = map { length $_ } ($A, $B, $C);
+   ($lA, $lB, $A, $B) = ($lB, $lA, $B, $A) if $lA > $lB;
+   return 0 if ($lA + $lB != $lC) || ($lB > $lA + 1);
+   my ($fA, $fB) = ($lA == $lB, 1); # can go first?
+   for my $i (0 .. $lB - 1) {
+      my ($cA, $cB) = map { substr $_, $i, 1 } ($A, $B);
+      my $sC = substr $C, 2 * $i, 2;
+      $fA &&= ($sC eq ($cA . $cB));
+      $fB &&= ($sC eq ($cB . $cA));
+      return 0 unless $fA || $fB;
+   }
+   return 1;
+}
+
+my $A = shift || 'XXY';
+my $B = shift || 'XXZ';
+my $C = shift || 'XXXXZY';
+say is_interleaving($A, $B, $C);