Are you using an older version of Perl? In perlfaq4 for 5.6.1 and 5.8.0, the is_numeric function looks like this (slightly different), and works correctly for your example:

sub getnum {
    use POSIX qw(strtod);
    my $str = shift;
    $str =~ s/^\s+//;
    $str =~ s/\s+$//;
    $! = 0;
    my($num, $unparsed) = strtod($str);
    if (($str eq '') || ($unparsed != 0) || $!) {
        return undef;
    } else {
        return $num;
    }
}

sub is_numeric { defined getnum($_[0]) }
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-- Mike

--
just,my${.02}