005#1 (functional)

1 files changed, 31 insertions, 0 deletions

diff --git a/005/ch1.pl b/005/ch1.pl
new file mode 100644
index 0000000..1d020a6
--- /dev/null
+++ b/005/ch1.pl
@@ -0,0 +1,31 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+# Functional implementation (tail-recursive)
+sub anagrams {
+	sub iter {
+		my ($word, @acc) = @_;
+		if (length($word) == 0) {
+			return @acc;
+		} else {
+			my ($head, $tail) = $word =~ /^(.)(.*)$/;
+			@_ = $tail; # Next word will be the tail of the previous one
+			foreach my $anagram (@acc) {
+				for (my $i = 0; $i <= length($anagram); $i++) {
+					push(@_, $anagram);
+					substr($_[-1], $i, 0) = $head;
+				}
+			}
+			goto &iter;
+		}
+	}
+	iter($_[0], (""));
+}
+
+for (@ARGV) {
+	for (anagrams($_)) {
+		print $_, "\n";
+	}
+}