Learning Perl, 5th Edition

Output to Standard Output

The print operator takes a list of values and sends each item (as a string, of course) to standard output in turn, one after another. It doesn’t add any extra characters before, after, or in between the items;^[*] if you want spaces between items and a newline at the end, you have to say so:

$name = "Larry Wall";
print "Hello there, $name, did you know that 3+4 is ", 3+4, "?\n";

Of course, that means that there’s a difference between printing an array and interpolating an array:

print @array;     # print a list of items
print "@array";   # print a string (containing an interpolated array)

That first print statement will print a list of items, one after another, with no spaces in between. The second one will print exactly one item, which is the string you get by interpolating @array into the empty string—that is, it prints the contents of @array, separated by spaces.^[†] So, if @array holds qw/ fred barney betty /,^[‡] the first one prints fredbarneybetty, while the second prints fred barney betty separated by spaces.

But before you decide to always use the second form, imagine that @array is a list of unchomped lines of input. That is, imagine that each of its strings has a trailing newline character. Now, the first print statement prints fred, barney, and betty on three separate lines. But the second one prints this:

 fred
  barney
  betty

Do you see where the spaces come from? Perl is interpolating an array, so it puts spaces between the elements. So, we get the first element ...