New Perl program

Author: rtoal

perl/README.md

@@ -10,6 +10,10 @@ Programs in this folder can be run from the command line like so:
 perl triple.pl
 ```
 
+```
+perl permutations.pl I like carrots
+```
+
 ```
 perl top_ten_scorers.pl < ../test/wnba_input
 ```
@@ -18,6 +22,7 @@ To run the tests on a Unix-like shell:
 
 ```
 ./test.sh
+
 ```
 
 ## About Perl

perl/permutations.pl

@@ -0,0 +1,18 @@
+use strict;
+use warnings;
+
+sub print_permutations {
+    my ($a, $n) = @_;
+    if ($n <= 0) {
+        print join("\t", @$a), "\n";
+    } else {
+        for my $i (0 .. $n - 1) {
+            print_permutations($a, $n - 1);
+            my $j = $n % 2 == 0 ? 0 : $i;
+            @$a[$j, $n] = @$a[$n, $j];
+        }
+        print_permutations($a, $n - 1);
+    }
+}
+
+print_permutations(\@ARGV, scalar(@ARGV) - 1);