要求：自定义输入一组字符串，例如 aa bb cc aa cc ，那么需要统计出各个字符串出现的次数。

#! /usr/bin/perl

my (@words, %count, $word);

chomp (@words=<STDIN>);

foreach $word (@words) {
  $count{$word} += 1;
}
foreach $word (keys %count) {
  print "$word was senn $count{$word} times.\n";
}