I think actually zero digits on the right side of the decimal point should not be allowed.

1234.

isn't what I think of as a number.

I would allow zero digits on the left side though.

.1234

seems ok by me. I think the 123 in

foo123foo

shouldn't be a number, so let's look for white space, or the beginning/end of the line before and after our match. The end check can be taken care of with lookahead (?=\s|$). Unfortunately you can't have variable length lookbehind, so (?<=\s|$) is impossible. So I just do (\s|^) and you should skip this register and take the next parenthesized group for your match.

Anyway we want to match all of these:

1234
1234.1234
.1234

but not

.
1234.
1234.1234.1234
.1234.1234
foo123foo
123.foo
foo.123
A regex that will do that is:

my $fixed_point_re = qr/(\s|^)((\d+(\.\d+)?)|(\.\d+))(?=\s|$)/;
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It's getting kind of hard to read, I realize, but it sits plays dead and fetches so...

Hope this helps!

Thomas.