Yes: of course this does not take care of the case when the given string has a length that is not a multiple of 5.
If you want to catch that, you can change the regex to /.{1,5}/g. 
perl -le 'print for "ABCDEFGHIJKLMNOPQRSTUVWXYZ" =~ /.{1,5}/g'
ABCDE
FGHIJ
KLMNO
PQRST
UVWXY
Z

[download]
Of course, depending on what it's used for, simply discarding it can be a better idea, and /.{5}/g works just fine for that.

In reply to Re^3: Split a string into items of constant length by truedfx
in thread Split a string into items of constant length by Anonymous Monk

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