use strict;
my $str = 'No protocol:
<p>youtube.com/watch?v=dQw4w9WgXcQ</p>
<p>www.youtube.com/watch?v=dQw4w9WgXcQ</p>
HTTP or HTTPS:
<p>http://youtube.com/watch?v=dQw4w9WgXcQ</p>
<p>http://www.youtube.com/watch?v=dQw4w9WgXcQ</p>
<p>https://youtube.com/watch?v=dQw4w9WgXcQ</p>
<p>https://www.youtube.com/watch?v=dQw4w9WgXcQ</p>
With or without “www”
<p>https://youtube.com/watch?v=dQw4w9WgXcQ</p>
<p>https://www.youtube.com/watch?v=dQw4w9WgXcQ</p>
Youtu.be short links
<p>youtu.be/LQaehcfXvK0</p>
<p>https://youtu.be/LQaehcfXvK0</p>
Embed Urls:
<p>http://www.youtube.com/embed/dQw4w9WgXcQ</p>
URLs with extra parameters:
<p>https://www.youtube.com/watch?v=LQaehcfXvK0&feature=youtu.be</p>
<p>https://www.youtube.com/watch?v=dQw4w9WgXcQ&list=RDdQw4w9WgXcQ&start_radio=1&t=1</p>
This URL won’t actually work on YouTube, but it works here, which is somewhat odd? And yet doesn\'t seem harmful.
<p>youtu.be/embed/dQw4w9WgXcQ</p>
Paragraph tags on separate lines with arbitrary whitespace:
<p>
www.youtube.com/embed/u8pCsfT1gDU
</p>
<p>
https://youtube.com/watch?v=dQw4w9WgXcQ
</p>
<p>
http://www.youtube.com/embed/dQw4w9WgXcQ
</p>
<p>
youtube.com/watch?v=dQw4w9WgXcQ
</p>
Paragraph tags with any other text in them, besides the URL:
<p>This shouldn’t work: https://youtube.com/watch?v=dQw4w9WgXcQ</p>
<p>https://youtube.com/watch?v=dQw4w9WgXcQ nor this</p>
<p>
https://youtube.com/watch?v=dQw4w9WgXcQ also not this
</p>
Paragraph tags with links added by markdown-it:
<p><a href="https://www.youtube.com/watch?v=dQw4w9WgXcQ">https://www.youtube.com/watch?v=dQw4w9WgXcQ</a></p>
<p>
<a href="https://www.youtube.com/watch?v=dQw4w9WgXcQ?something" class="something" id="whatever">
youtube.com/watch?v=dQw4w9WgXcQ?foo=bar&whatever
</a>
</p>
';
my $regex = qr/<p>(\s*)(<a(.*)>)?(\s*)(https?:\/\/)?(w{3}\.)?(youtube\.com|youtu\.be)\/(watch\?v=|embed\/)?([A-Za-z0-9-_]{11})(\S*)(\s*)(<\/a>)?(\s*)<\/p>/p;
if ( $str =~ /$regex/g ) {
print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n";
# print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n";
# print "Capture Group 2 is $2 ... and so on\n";
}
# ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p'
# Named capture groups can be called via $+{name}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html