Edition 3 of Programming Perl says on page 59 that "To convert from string to number, Perl internally uses something like the C library's atof(3) function."

It's possible that the perl on the unix box giving you problems is using a buggy (or stricter) atof.

I think the atof implementation is now rolled into perl, but I'm not sure. On older versions, it was probably a library call.

Edit: HAHA! Reading the p5p summary on use.perl.org today, I got this Larry Wall quote as a random tagline:

There are many times when you want it to ignore the rest of the string just like atof() does. Oddly enough, Perl calls atof(). How convenient. :-)
--Larry Wall in <1991Jun24.231628.14446@jpl-devvax.jpl.nasa.gov>

It's a very old quote, so perl might not use atof any more, but it was still a funny (to me) coincidence.
--
Mike