Sometimes it's best to start simple with these things. Here's an alternate approach that seems to do what you seem to want done: 

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @test = qw(RC1XY  RS);
 ;;
 for my $s (@test) {
   printf qq{'$s' -> };
   my ($p_r, $d1, $p_mc, $p_new_mc) = $s =~ m{
     ([[:upper:]]+) (?: (\d+) ([[:upper:]]) ([[:upper:]]))?
     }xms;
   dd $p_r, $d1, $p_mc, $p_new_mc;
   }
"
'RC1XY' -> ("RC", 1, "X", "Y")

'RS' -> ("RS", undef, undef, undef)

[download]
How does this match your basic requirements? What further elaborations and sophistications are needed? Do you really need named captures? Etc... (Update: You mention that you're using Perl 5.10, but both these examples, above and below, run the same for me under 5.8.9 and 5.14.4 as well as 5.10.1.)

Update: I notice you write that you want a "blank" (which I take to be an empty string) to be produced for sub-patterns that do not match. You will note that the example above yields undefined values for non-matching sub-patterns. Since the empty string and undef both have a false boolean value, I find it is usually just as easy to test and deal with undefs as with empty strings and so I usually avoid the extra effort to produce an empty string. If you really need them, here's a possible alternative approach: 

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @test = qw(RC1XY  RS);
 ;;
 for my $s (@test) {
   printf qq{'$s' -> };
   my ($p_r, $d1, $p_mc, $p_new_mc) = $s =~ m{
     ([[:upper:]]+) (\d*) ([[:upper:]]?) ([[:upper:]]?)
     }xms;
   dd $p_r, $d1, $p_mc, $p_new_mc;
   }
"
'RC1XY' -> ("RC", 1, "X", "Y")

'RS' -> ("RS", "", "", "")

[download]

In reply to Re^3: Question on Regular Expression by AnomalousMonk
in thread Question on Regular Expression by sjain

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