##  syntax errors

{{		abcdef		/Missing closing braces/	unterminated closure
\1		abcdef		/reserved/			back references
\x[		abcdef		/Missing close bracket/		unterminated \x[..]
\X[		abcdef		/Missing close bracket/		unterminated \X[..]

* abc		abcdef		/Quantifier follows nothing/	bare * at start
  * abc		abcdef		/Quantifier follows nothing/	bare * after ws
[*|a]		abcdef		/Quantifier follows nothing/	bare * after [
[ *|a]		abcdef		/Quantifier follows nothing/	bare * after [+sp
[a|*]		abcdef		/Quantifier follows nothing/	bare * after |
[a| *]		abcdef		/Quantifier follows nothing/	bare * after |+sp

+ abc		abcdef		/Quantifier follows nothing/	bare + at start
  + abc		abcdef		/Quantifier follows nothing/	bare + after ws
[+|a]		abcdef		/Quantifier follows nothing/	bare + after [
[ +|a]		abcdef		/Quantifier follows nothing/	bare + after [+sp
[a|+]		abcdef		/Quantifier follows nothing/	bare + after |
[a| +]		abcdef		/Quantifier follows nothing/	bare + after |+sp

? abc		abcdef		/Quantifier follows nothing/	bare ? at start
  ? abc		abcdef		/Quantifier follows nothing/	bare ? after ws
[?|a]		abcdef		/Quantifier follows nothing/	bare ? after [
[ ?|a]		abcdef		/Quantifier follows nothing/	bare ? after [+sp
[a|?]		abcdef		/Quantifier follows nothing/	bare ? after |
[a| ?]		abcdef		/Quantifier follows nothing/	bare ? after |+sp

: abc		abcdef		/Quantifier follows nothing/	bare : at start
  : abc		abcdef		/Quantifier follows nothing/	bare : after ws
[:|a]		abcdef		/Quantifier follows nothing/	bare : after [
[ :|a]		abcdef		/Quantifier follows nothing/	bare : after [+sp
[a|:]		abcdef		/Quantifier follows nothing/	bare : after |
[a| :]		abcdef		/Quantifier follows nothing/	bare : after |+sp

		abcdef		/'Null pattern'/		null pattern
  		abcdef		/'Null pattern'/		ws null pattern

  =abc		abcdef		/LHS of alias must be lvalue/	bare : after ws
[ =a]		abcdef		/LHS of alias must be lvalue/	bare : after [+sp
[a| =a]		abcdef		/LHS of alias must be lvalue/	bare : after |+sp

\b          abcdef      /Unsupported/                   bare \b
\B          abcdef      /Unsupported/                   bare \B