As perusual, ikegami has provided a profound solution to the problem which makes further comments superfluous - or plainly embarrassing. I still venture to contribute my humble solution, not because I think it is better but because it takes another line of attack to the problem.

How about:

my @array = ( 12, 123456, 134, 3, 45678901, 55555, 3434, 1122334455 );

my @long = ( join " ", @array ) =~ /[^ ]{5,}/g;

print join "\n", @long;
[download]

This will return:

123456
45678901
55555
1122334455
[download]

Is this what you were after? As for performance, I have no idea how this compares to ikegami's solution. Any insights on this?

Cheers -

Pat