G'day Rob,

$ alias perle
alias perle='perl -Mstrict -Mwarnings -Mautodie=:all -MCarp::Always -E
+'
[download]

There are only a limited number of "Numeric_Value" values. They can be positive, negative and fractional but 3.12e-03 is not one of them. In perluniprops, a search for "Numeric_Value" finds 146 matches. Some examples (in spoiler):

See [PDF] "4.6 Numeric Value" from the Unicode specification.

Here's a quick script you can use to check code points:

#!/usr/bin/env perl

use strict;
use warnings;

use Unicode::UCD 'charprop';

for my $char (0, 1, ' ', 'a', "\n") {
    print "Char '$char'\n";
    my $code_point = ord $char;
    print 'Numeric_Type:  ', charprop($code_point, 'Numeric_Type'), "\
+n";
    print 'Numeric_Value:  ', charprop($code_point, 'Numeric_Value'), 
+"\n";
    print '-' x 40, "\n";
}
[download]

Output (in spoiler):

Char '0'
Numeric_Type:  Decimal
Numeric_Value:  0
----------------------------------------
Char '1'
Numeric_Type:  Decimal
Numeric_Value:  1
----------------------------------------
Char ' '
Numeric_Type:  None
Numeric_Value:  NaN
----------------------------------------
Char 'a'
Numeric_Type:  None
Numeric_Value:  NaN
----------------------------------------
Char '
'
Numeric_Type:  None
Numeric_Value:  NaN
----------------------------------------
[download]

That might be sufficient information for your needs. I was going to look in "lib/unicore/TestProp.pl" but I can't locate it: I tried https://github.com/Perl/perl5/tree/blead/lib/unicore, https://github.com/Perl/perl5/tree/maint-5.34/lib/unicore, and ran `find /home/ken/perl5/perlbrew/perls/ -iname TestProp.pl` on my computer. If you want, and provide a link, I'll be happy to check it out.