use strict;
use warnings;

my @list = qw( R1U1
R2U3
R10U1
R10-U1
R2-U2
R3-U13
R10-U5
R2
);

@list = sort special_compare @list;

print "$_\n" for @list;

sub special_compare
{
    my (@myA) = $a =~ /([a-zA-z_]+|\d+)/g;
    my (@myB) = $b =~ /([a-zA-z_]+|\d+)/g;
    
    my $result=0;
    
    my $Atoken;
    my $Btoken;
    
    while ( defined ($Atoken = shift @myA) and defined ($Btoken = shift @myB)
           and $result == 0)
    {   
       $result = ($Atoken cmp $Btoken);     
    }
    
    if ($result ==0) #if one array "runs out", longest is "greater"
    {
        return -1 if (@myA < @myB);
        return 1  if (@myA > @myB);
    }
    return $result;    
}

__END__
R1U1
R10U1
R10-U1
R10-U5
R2
R2-U2
R2U3
R3-U13