add perl solution for wk-081 ch-2

1 files changed, 53 insertions, 0 deletions

diff --git a/challenge-081/alexander-pankoff/perl/ch-2.pl b/challenge-081/alexander-pankoff/perl/ch-2.pl
new file mode 100644
index 0000000000..c560ba5cac
--- /dev/null
+++ b/challenge-081/alexander-pankoff/perl/ch-2.pl
@@ -0,0 +1,53 @@
+#!/usr/bin/env perl
+use v5.20;
+use utf8;
+use strict;
+use warnings;
+use autodie;
+use feature qw(say signatures);
+no warnings 'experimental::signatures';
+
+use List::Util qw(reduce);
+
+run_challenge();
+
+sub run_challenge() {
+    my ($input_file) = @ARGV;
+    my $frequencies_to_words =
+      frequency_sort( words( sanitize_input( read_file($input_file) ) ) );
+    print_word_frequencies($frequencies_to_words);
+}
+
+sub print_word_frequencies($frequencies) {
+    say join( ' ', $_, @{ $frequencies->{$_} } )
+      for sort { $a <=> $b } keys %{$frequencies};
+}
+
+sub frequency_sort(@words) {
+    my %word_count;
+    $word_count{$_}++ for @words;
+    my %frequencies;
+    push @{ $frequencies{ $word_count{$_} } }, $_ for sort keys %word_count;
+
+    return \%frequencies;
+}
+
+# split the given string into words
+sub words($str) {
+    return split( /\s+/, $str );
+}
+
+# replace illegal chars with whitespace
+sub sanitize_input($input) {
+    return $input =~ s/[\."\(\),]|--|'s/ /rg;
+}
+
+# read the whole file
+sub read_file($filename) {
+    local $/ = undef;
+    open( my $fh, '<', $filename );
+    my $out = <$fh>;
+    close($fh);
+    return $out;
+}
+