I think your logical statement can be restated as "a line made only of digits, at least 5 digits long", and in that case the regular expression you need is

/^\d{5,}$/
[download]

You could add a \s* right before the $ if you want to allow for spaces at the end.

Or if you want to allow both digits and spaces, you could use:

/^\d{5,}[\d\s]*$/
[download]

--ZZamboni, aka Duke Dong