In the code you just posted you have removed the single-quotes around _EOF_. This will prompt Perl to interpolate any perl-looking variable (for example a word prepended by sigils: $ or @ etc.) within the heredoc content. But now you have none. Try adding, in a new line, echo "i will cp '$source' '$dest'" and see what happens.

Note: in your posts, please enclose all code within <c> ... </c> tags because most of us in here are humans, not machines.