I think this may depend on the browser, but I can't test cause I can't find the setting in Display Settings ... ?

edit

Or is it just a CSS hack?

update

OK found it hidden in the help page...




• Code Prefix: whatever you enter here will be used as a prefix for lines inside <code> blocks. If you specify something that matches /&\d+;/, then those digits will be incremented for each line of code. Typically you would specify &001;: to have all code lines numbered starting from 001.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

PS: Je suis Charlie!

OK, I investigated my settings. I use a CSS + JS solution (it links to CodeMirror). When I remove it and add the Code Prefix, the line numbers get selected with the code.
لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

This would block C&P without clicking on DOWNLOAD, that's why many would object. But an interactive JS toggle might solve that.

Hmm , firefox doesn't copy/paste line numbers ... so I don't think JS is required

1. #!/usr/bin/perl --
2. use strict;
3. use warnings;

4. print "Hello 
   + world!\n";