What is the correct way to break a line of Perl code into two?

In Perl, a carriage return will serve in any place where a regular space does. Backslashes are not used like in some languages; just add a CR.

You can break strings up over multiple lines with concatenation or list operations:

print "this is ",
    "one line when printed, ",
    "because print takes multiple ",
    "arguments and prints them all!\n";
print "however, you can also " .
    "concatenate strings together " .
    "and print them all as one string.\n";

print <<DOC;
But if you have a lot of text to print,
you can use a "here document" and create
a literal string that runs until the
delimiter that was declared with <<.
DOC
print "..and now we're back to regular code.\n";

You can read about here documents in in perldoc perlop.