Hi,
This is also non destructive, and uses a regexp:

( $_ = $genome1 ) =~ s/(.{60})/print $1."\n"/eg;
[download]

Note the print statement in the regex using the e flag.

I don't know which is the most performant, but I do think that substr is more performant than a plain regex.
But regexes are more fun :-)
---------------------------
Dr. Mark Ceulemans
Senior Consultant
IT Masters, Belgium