my @eatables = ("fruit", "meat", "vegetable");
open(FH, "<sample.txt")  or die "Can't open sample.txt: $!";

sub main(){
 my $hash = {"fruit" => 0, "meat" => 0, "vegetable" => 0};
 while(my $line = <FH>){
     foreach(@eatables){
        if($line =~ m/$_/){
             print "found: $_ at line $.\n";
             $hash->{$_}++;
         }
     }
 }

 foreach(keys%{$hash}) {
  print "not found : $_" if $hash->{$_} == 0 ;
 }

 close(FH);
}

这样你就可以知道每根弦有几个音。

#!/usr/bin/perl
use strict;

my @eatables        = ("fruit", "meat", "vegetable");
my ($combined_search, $not_found) = (join("|",@eatables)) x 2;

sub main() {
       while(my $line = <STDIN>) {
              $line =~ /($combined_search)/ ;
              print "\nFound: $1";
              $not_found =~ s/$1//g; 
        }
}

  main();
  print "Not found: $not_found";