c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = '';
 my $r = '';
 my @add = qw(a b c X d e Y f g h);
 ;;
 my $xeger = qr{ \A Y .* X }xms;
 ;;
 while (@add){
   print qq{'$s' }, $r =~ $xeger ? 'MATCH' : \"no match\";
   $r  = qq{$add[0]$r};
   $s .= shift @add;
   }
"
'' no match
'a' no match
'ab' no match
'abc' no match
'abcX' no match
'abcXd' no match
'abcXde' no match
'abcXdeY' MATCH
'abcXdeYf' no match
'abcXdeYfg' no match