c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -e
"my @test = qw(RC1XY RS RW12QW1X FOO FOOx FOO23PQ xFOO23PQXXX foo xyzzy);
 ;;
 for my $s (@test) {
   printf qq{'$s' -> };
   if (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;
     }
   else {
     print qq{no match \n};
     }
   }
"
'RC1XY' -> ("RC", 1, "X", "Y")
'RS' -> ("RS", "", "", "")
'RW12QW1X' -> ("RW", 12, "Q", "W")
'FOO' -> ("FOO", "", "", "")
'FOOx' -> ("FOO", "", "", "")
'FOO23PQ' -> ("FOO", 23, "P", "Q")
'xFOO23PQXXX' -> ("FOO", 23, "P", "Q")
'foo' -> no match
'xyzzy' -> no match