I was reading the Perl docs on heredoc just now, and found one description that I found very confusing. I'm hoping you can help me understand what's being described here: http://perldoc.perl.org/perlop.html#Quote-Like-Operators

Specifically, this part:

If you use a here-doc within a delimited construct, such as in s///eg, the quoted material must come on the lines following the final delimiter. So instead of

    s/this/<<E . 'that'
    the other
    E
     . 'more '/eg;
[download]

you have to write

    s/this/<<E . 'that'
     . 'more '/eg;
    the other
    E
[download]

I understand the part about placing the heredoc after the s// construct, but the substitution itself is confusing. Does it mean the same as this?

s/this/the other\nthatmore /eg;
[download]

I guess I'm wrong to assume those periods are concatenation operators, but if so, what's going on here? What's the use case?

Thanks very much in advance!