问使用perl替换文件行中多次出现的单词

EN

#!/usr/bin/perl

use strict;

use warnings;

use Tie::File;

my $string2 = 'first_part';

my $string3 = 'middle_part';

my $string4 = 'last_part';

my @contents=();

tie @contents, 'Tie::File','test.html' or die "Not able to Tie test.html\n";

my $count=1;

foreach (@contents)

{

my $string = $_;

my $quoted_substring = quotemeta($string);

my $before = 'test_example_start';

my $after  = 'text_example_end';

if ($string =~ /\Q$before\E(.*?)\Q$after\E/) {

my $finalstr = "$string2$1$string3$1$string4"; 

s/$quoted_substring/$finalstr/g;


 print $finalstr;  

} 
        $count++;

    my $finalstr ='';

}

untie @contents;

test_example_start this is lesson-1 text_example_end where everyone attended the class test_example_start this is lesson-2 text_example_end where two members attended the class test_example_start this is lesson-3 text_example_end where five members attended the class

first_part this is lesson-1 middle_part this is lesson-1 last_part where everyone attended the class first_part this is lesson-2 middle_part this is lesson-1 last_part where two members attended the class first_part this is lesson-1 middle_part this is lesson-3 last_part where five members attended the class

first_part this is lesson-1 middle_part this is lesson-1 last_part