#!/usr/bin/env perl
use warnings;
use strict;

my $x = "0.01 NaN 2.30 4.44";

# the following works as desired
my $r1 = qr/([Na0-9\.\-\+]+)\s+
        ([Na0-9\.\-\+]+)\s+
        ([Na0-9\.\-\+]+)\s+
        ([Na0-9\.\-\+]+)/x;
my ($d, $e, $f, $g) = ($x =~ m/$r1/x );
print "good: $d, $e, $f, $g\n";

# recursive subpatterns
my $rx = qr{ ([Na0-9\.\-\+]+)
	\s+ ((?1)) \s+ ((?1)) \s+ ((?1)) }x;
($d, $e, $f, $g) = $x =~ $rx or die;
print "good? $d, $e, $f, $g\n";

# or match / validate first, then split
my $ry = qr{ ([Na0-9\.\-\+]+) (?: \s+ (?1)){3} }x;
$x =~ $ry or die;
($d, $e, $f, $g) = split ' ', $&;
print "good? $d, $e, $f, $g\n";