use strict; use warnings; use feature qw/ say /;
use Data::Dumper; $Data::Dumper::Sortkeys = 1;

use Path::Tiny;

my $root_dir = Path::Tiny->tempdir;

_populate_for_demo( $root_dir );

my $re = qr/ (?:\w|\d)+ _ \w+ _ .+ _R(1|2)_ .+ /x;

my %results;

$root_dir->visit(
    sub { $_->is_file and push @{ $results{$1} }, "$_" if /$re/ },
    { recurse => 1 },
);

say Dumper \%results;

exit;

sub _populate_for_demo {
    my $temp_dir = shift;
    path("$temp_dir/$_/aa_bb_cc_R1_dd.tmp")->touchpath for 'foo','bar';
    path("$temp_dir/$_/aa_bb_cc_R2_dd.tmp")->touchpath for 'baz','qux';
    return $temp_dir;
}

__END__