intuit_more: no need to copy before keyword check

That also avoids crashing on overrun.

Author: hvds

t/re/pat.t

@@ -22,7 +22,7 @@ BEGIN {
     skip_all_without_unicode_tables();
 }
 
-plan tests => 757;  # Update this when adding/deleting tests.
+plan tests => 759;  # Update this when adding/deleting tests.
 
 run_tests() unless caller;
 
@@ -1626,6 +1626,15 @@ EOP
         like("TffffffffffffT\x{100}TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT5TTTTTTTTTTTTTTTTTTTTTTTTT3TTgTTTTTTTTTTTTTTTTTTTTT2TTTTTTTTTTTTTTTTTTTTTTTHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHiHHHHHHHfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff&ffff", qr/TffffffffffffT\x{100}TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT5TTTTTTTTTTTTTTTTTTTTTTTTT3TTgTTTTTTTTTTTTTTTTTTTTT2TTTTTTTTTTTTTTTTTTTTTTTHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHiHHHHHHHfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff&ffff/il, "");
     }
 
+	{	# [perl #123604]
+		my($s, $x, @x) = ('abc', 'a', 'd');
+		my $long = 'b' x 2000;
+		my $eval = q{$s =~ m{$x[bbb]c} ? 1 : 0};
+		$eval =~ s{bbb}{$long};
+		my $match = eval $eval;
+		ok(1, "did not crash");
+		ok($match, "[bbb...] resolved as character class, not subscript");
+	}
 } # End of sub run_tests
 
 1;

toke.c

@@ -3827,11 +3827,10 @@ S_intuit_more(pTHX_ char *s)
 		    && !(last_un_char == '$' || last_un_char == '@'
 			 || last_un_char == '&')
 		    && isALPHA(*s) && s[1] && isALPHA(s[1])) {
-		    char *d = tmpbuf;
+		    char *d = s;
 		    while (isALPHA(*s))
-			*d++ = *s++;
-		    *d = '\0';
-		    if (keyword(tmpbuf, d - tmpbuf, 0))
+			s++;
+		    if (keyword(d, s - d, 0))
 			weight -= 150;
 		}
 		if (un_char == last_un_char + 1)