your solution works but is slower than just appending a "\n" to the end during the final map

If pack is faster — seems odd — you could use Z instead of A.

Ah, that's tricky. I suppose you're right, though. Do you know if there's a web-browsable version of the Perl source code anywhere I could check into that?

http://perl5.git.perl.org/perl.git Look for pp_unpack in pp*.c (probably pp.c specifically pp_pack.c).

The relevant code:

1458                     for (ptr = s+len-1; ptr >= s; ptr--)
1459                         if (*ptr != 0 && !isSPACE(*ptr)) break;
1460                     ptr++;
[download]

and

#define isSPACE(c) \
        ((c) == ' ' || (c) == '\t' || (c) == '\n' || (c) =='\r' || (c)
+ == '\f')
[download]

aka \s

Update: Added relevant code.