"most of the times if javascript gives me hard time i just declare it in perl script then i just call it in html as string. and works
something which is very simple, and most dont think about it that can fix problem"

More than once in the thread people have suggested separating your perl code from your HTML/JavaScript/CSS, because this makes life simpler. HTML::Template would be a start, several of the linked tutorials use this. Modern frameworks like Mojolicoius::Lite provide more options, for example templates that allow embedding perl code in a clean and sensible manner, among a saner path for web development.