perl extract text between html tags using regex

Note: Do not use regular expressions to parse HTML.

This first option is done using HTML::TreeBuilder, one of many HTML Parsers that is available to use. You can visit the link provided above and read the documentation and see the example's that are given.

use strict;
use warnings;
use HTML::TreeBuilder;

my $str 
   = "<ul>"
   . "<li>hello</li>"
   . "<li>there</li>"
   . "<li>everyone</li>"
   . "</ul>"
   ;

# Now create a new tree to parse the HTML from String $str
my $tr = HTML::TreeBuilder->new_from_content($str);

# And now find all <li> tags and create an array with the values.
my @lists = 
      map { $_->content_list } 
      $tr->find_by_tag_name('li');

# And loop through the array returning our values.
foreach my $val (@lists) {
   print $val, "\n";
}

If you decide you want to use a regular expression here (I don't recommend). You could do something like..

my $str
   = "<ul>"
   . "<li>hello</li>"
   . "<li>there</li>"
   . "<li>everyone</li>"
   . "</ul>"
   ;

my @matches;
while ($str =~/(?<=<li>)(.*?)(?=<\/li>)/g) {
  push @matches, $1;
}

foreach my $m (@matches) {
   print $m, "\n";
}

Output:

hello
there
everyone

Note: Do not use regular expressions to parse HTML.

hwnd has already provided one HTML Parser solution.

However, for a more modern HTML Parser based off css selectors, you can check out Mojo::DOM. There is a very informative 8 minute intro video at Mojocast episode 5.

use strict;
use warnings;

use Mojo::DOM;

my $html = do {local $/; <DATA>};

my $dom = Mojo::DOM->new($html);

for my $li ($dom->find('li')->text->each) {
    print "$li\n";
}

__DATA__
<ul>
  <li>hello</li>
  <li>there</li>
  <li>everyone</li>
</ul>

Outputs:

hello
there
everyone