It seems match the last 'key => value' first, i try the below code serval times, but got the same output.

use strict;
use warnings;

use Data::Dumper;

my $b =  'test  200';
my %hash = (
          c => ( $b =~ /([a-z]+)/ ? $& : 0 ),
          b => ( $b =~ /(\d+)/ ? $` : 0 ),
          a => ( $b =~ /\s+/ ? $' : 0 ),
        );

print Dumper(\%hash);
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Output:

$VAR1 = {
          'c' => '  ',
          'a' => '200',
          'b' => 'test'
        };
[download]