"When an array is interpolated into a string, perl automagically does a join with the default record separator, which also happens to default to a space."

Close.

The 'default record separator' (i think you mean the input record separator, $/, which defaults to a new line) is not used here, instead the list separator ($", which defaults to a space) is used. See perlvar for more. Also, page 13 of Network Programming w/ Perl lays out the scoop on end-of-line characters. If you don't have a copy (which you should), you can read a watered-down version of that discussion here: A Little History on 0D0A.

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)