use strict;
use warnings;

use Data::Dumper;

my $raStruct = [
   [ qw{null 44 4} ],
   [ qw{6 24 6} ],
   ];

print Data::Dumper->Dump([$raStruct], [q{raStruct}]);

my $test = q{xray};

map { $_->[0] =~ s/[^0-9]+/$test/ } @$raStruct;

print Data::Dumper->Dump([$raStruct], [q{raStruct}]);

##</code><code>##

$raStruct = [
              [
                'null',
                '44',
                '4'
              ],
              [
                '6',
                '24',
                '6'
              ]
            ];
$raStruct = [
              [
                'xray',
                '44',
                '4'
              ],
              [
                '6',
                '24',
                '6'
              ]
            ];