c:\@Work\Perl\monks>perl -wMstrict -le
"my @X = ('aX-raya', 'aX raya', 'aXraya', 'axraya', 'X Ray', 'aXYraya');
 ;;
 print 'placeholder matching:';
 for my $s (@X) {
   printf qq{'$s' -> };
   if ($s =~ m{ X . ray }xms) {
     print 'match';
     }
   else {
     print 'NO match';
     }
   }
"
placeholder matching:
'aX-raya' -> match
'aX raya' -> match
'aXraya' -> NO match
'axraya' -> NO match
'X Ray' -> NO match
'aXYraya' -> match