word_freq.pl in Perl

A word-frequency report over an inline passage, driven by one hash.

use strict;
use warnings;

# word_freq: count word occurrences in an inline passage

my $text = <<'TEXT';
The quick brown fox jumps over the lazy dog.
The dog barks; the fox runs. Quick thinking, that fox.
TEXT

my @words = lc($text) =~ /[a-z]+/g;

my %freq;
$freq{$_}++ for @words;

printf "words total: %d\n", scalar @words;
printf "words unique: %d\n", scalar keys %freq;

my @ranked = sort { $freq{$b} <=> $freq{$a} or $a cmp $b } keys %freq;

print "top 5:\n";
for my $word (@ranked[0 .. 4]) {
    printf "  %-8s %d\n", $word, $freq{$word};
}

my @once = sort grep { $freq{$_} == 1 } keys %freq;
print "seen once: ", join(", ", @once), "\n";

How it works

1. A list-context match, lc($text) =~ /[a-z]+/g, pulls every lowercase word.
2. $freq{$_}++ for @words builds the whole frequency table in one line.
3. A two-key sort ranks by count, then alphabetically to break ties.
4. grep { $freq{$_} == 1 } filters out the words seen only once.

Keywords and builtins used here

• for
• grep
• join
• keys
• lc
• my
• print
• printf
• scalar
• sort
• use

The run, in numbers

Lines

27

Characters to type

642

Tokens

155

Three-star pace

80 tpm

At the three-star pace of 80 tokens a minute, this run takes about 116 seconds.

Type this snippet

Step 1 of 3 in Encore, step 25 of 27 in Language basics.

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