diff --git a/runtime/syntax/generator/vim.vim.base b/runtime/syntax/generator/vim.vim.base
index 4666d71..883056b 100644
--- a/runtime/syntax/generator/vim.vim.base
+++ b/runtime/syntax/generator/vim.vim.base
@@ -3,7 +3,7 @@
 " Maintainer:	   Hirohito Higashi <h.east.727 ATMARK gmail.com>
 "	   Doug Kearns <dougkearns@gmail.com>
 " URL:	   https://github.com/vim-jp/syntax-vim-ex
-" Last Change:	   2024 Jul 18
+" Last Change:	   2024 Aug 16
 " Former Maintainer: Charles E. Campbell
 
 " DO NOT CHANGE DIRECTLY.
@@ -525,7 +525,13 @@
 syn match	vimUnletBang	contained	"!"	skipwhite nextgroup=vimUnletVars
 syn region	vimUnletVars	contained	start="$\I\|\h" skip="\n\s*\\" end="$" end="|" contains=vimVar,vimEnvvar,vimContinue,vimString,vimNumber
 
-VimFoldh syn region vimLetHereDoc	matchgroup=vimLetHereDocStart start='=<<\s*\%(trim\s\+\%(eval\s\+\)\=\|eval\s\+\%(trim\s\+\)\=\)\=\z(\L\S*\)' matchgroup=vimLetHereDocStop end='^\s*\z1\s*$' extend
+" Note: This incorrectly matches end markers with leading whitespace even if
+"       "trim" was not specified.  Matching :let indent for "trim" indented
+"       end markers would require a contained :let that cannot be restricted
+"       to the start pattern.  A common internal testing use of heredocs is to
+"       specify code blocks where :let commonly appears in the heredoc text.
+VimFoldh syn region vimLetHereDoc	matchgroup=vimLetHereDocStart start='=<<\s*\%(trim\s\+\)\=\z(\L\S*\)'		             matchgroup=vimLetHereDocStop end='^\s*\z1$' extend
+VimFoldh syn region vimLetHereDoc	matchgroup=vimLetHereDocStart start='=<<\s*\%(trim\s\+\)\=eval\s\+\|eval\s\+\%(trim\s\+\)\=\z(\L\S*\)' matchgroup=vimLetHereDocStop end='^\s*\z1$' contains=vimStringInterpolationExpr,vimStringInterpolationBrace extend
 
 Vim9 syn keyword	vim9Const	const	skipwhite nextgroup=vim9Variable,vim9VariableList
 Vim9 syn keyword	vim9Final	final	skipwhite nextgroup=vim9Variable,vim9VariableList
diff --git a/runtime/syntax/testdir/dumps/vim_ex_function_fold_05.dump b/runtime/syntax/testdir/dumps/vim_ex_function_fold_05.dump
index 5511d0d..88ca355 100644
--- a/runtime/syntax/testdir/dumps/vim_ex_function_fold_05.dump
+++ b/runtime/syntax/testdir/dumps/vim_ex_function_fold_05.dump
@@ -17,4 +17,4 @@
 @75
 |++0#0000e05#a8a8a8255|-@1| @1|5| |l|i|n|e|s|:| |f|u|n|c|t|i|o|n| |F|o@1|(|)|-@46
 | +0#0000000#ffffff0@74
-@57|1|4|3|,|0|-|1| @6|7|3|%| 
+@57|1|4|3|,|0|-|1| @6|7|4|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_function_fold_06.dump b/runtime/syntax/testdir/dumps/vim_ex_function_fold_06.dump
index 8925be9..a2f73a0 100644
--- a/runtime/syntax/testdir/dumps/vim_ex_function_fold_06.dump
+++ b/runtime/syntax/testdir/dumps/vim_ex_function_fold_06.dump
@@ -14,7 +14,7 @@
 | +0#0000000#ffffff0@74
 |++0#0000e05#a8a8a8255|-@1| @1|3| |l|i|n|e|s|:| |f|u|n|c|t|i|o|n| |F|o@1|(|)|-@46
 | +0#0000000#ffffff0@74
-|++0#0000e05#a8a8a8255|-@1| @1|6| |l|i|n|e|s|:| |f|u|n|c|t|i|o|n| |F|o@1|(|)|-@46
+|++0#0000e05#a8a8a8255|-@1| @1|5| |l|i|n|e|s|:| |f|u|n|c|t|i|o|n| |F|o@1|(|)|-@46
 | +0#0000000#ffffff0@74
 |++0#0000e05#a8a8a8255|-@1| @1|5| |l|i|n|e|s|:| |f|u|n|c|t|i|o|n| |F|o@1|(|)|-@46
 | +0#0000000#ffffff0@56|1|8|0|,|1| @8|9|1|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_function_fold_07.dump b/runtime/syntax/testdir/dumps/vim_ex_function_fold_07.dump
index 393afe7..7a93653 100644
--- a/runtime/syntax/testdir/dumps/vim_ex_function_fold_07.dump
+++ b/runtime/syntax/testdir/dumps/vim_ex_function_fold_07.dump
@@ -17,4 +17,4 @@
 |~| @73
 |~| @73
 |~| @73
-| +0#0000000&@56|2@1|0|,|0|-|1| @6|B|o|t| 
+| +0#0000000&@56|2|1|9|,|0|-|1| @6|B|o|t| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_00.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_00.dump
new file mode 100644
index 0000000..2e3d0e6
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_00.dump
@@ -0,0 +1,20 @@
+| +0#0000e05#a8a8a8255@1>"+0&#ffffff0| |V|i|m| |:|l|e|t| |h|e|r|e|d|o|c| |c|o|m@1|a|n|d| +0#0000000&@46
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |V|I|M|_|T|E|S|T|_|S|E|T|U|P| |l|e|t| |g|:|v|i|m|s|y|n|_|f|o|l|d|i|n|g| |=| |"+0#e000002&|h|"| +0#0000000&@29
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |V|I|M|_|T|E|S|T|_|S|E|T|U|P| |s|e|t|l| |f|d|c|=|2| |f|d|l|=|9@1| |f|d|m|=|s|y|n|t|a|x| +0#0000000&@27
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |E|N|D| +0#0000000&@57
+||+0#0000e05#a8a8a8255| |l+0#e000002#ffffff0|i|n|e|1| +0#0000000&@67
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+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
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+||+0#0000e05#a8a8a8255| |l+0#e000002#ffffff0|i|n|e|1| +0#0000000&@67
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+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@52
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|1| +0#0000000&@65
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|2| +0#0000000&@65
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+@57|1|,|1| @10|T|o|p| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_01.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_01.dump
new file mode 100644
index 0000000..6e38ae7
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_01.dump
@@ -0,0 +1,20 @@
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@52
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|1| +0#0000000&@65
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|2| +0#0000000&@65
+||+0#0000e05#a8a8a8255| >E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| | +0#0000000#ffffff0@1|l+0#af5f00255&|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@50
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+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |i|n|t|e|r|p|o|l|a|t|i|o|n| +0#0000000&@57
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
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+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+@57|1|9|,|1| @9|1|3|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_02.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_02.dump
new file mode 100644
index 0000000..3613d10
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_02.dump
@@ -0,0 +1,20 @@
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| | +0#0000000#ffffff0@1|l+0#af5f00255&|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |e|v|a|l| |E|N|D| +0#0000000&@50
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+||+0#0000e05#a8a8a8255| >E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |e|v|a|l| |E|N|D| +0#0000000&@47
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+||+0#0000e05#a8a8a8255| | +0#e000e06#ffffff0@1|E|N|D| +0#0000000&@67
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |n|o| |i|n|t|e|r|p|o|l|a|t|i|o|n| |(|e|s|c|a|p|e|d| |{| |a|n|d| |}|)| +0#0000000&@36
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+@57|3|7|,|1| @9|3|1|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_03.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_03.dump
new file mode 100644
index 0000000..de3f8fe
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_03.dump
@@ -0,0 +1,20 @@
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
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+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1> +0#0000000#ffffff0@72
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+@57|5@1|,|0|-|1| @7|5|0|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_04.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_04.dump
new file mode 100644
index 0000000..c6d1b4d
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_04.dump
@@ -0,0 +1,20 @@
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+||+0#0000e05#a8a8a8255| | +0#e000e06#ffffff0@1|E|N|D| +0#0000000&@67
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+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
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+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@52
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|{|1| |+| |0|}| +0#0000000&@59
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|{|1| |+| |1|}| +0#0000000&@59
+@57|7|3|,|0|-|1| @7|6|9|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_05.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_05.dump
new file mode 100644
index 0000000..e66d1cc
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_05.dump
@@ -0,0 +1,20 @@
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1|l|i|n|e|{|1| |+| |1|}| +0#0000000&@59
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|-+0#0000e05#a8a8a8255| | +0#0000000#ffffff0@1|l+0#af5f00255&|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@50
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@3|l|i|n|e|{|1| |+| |0|}| +0#0000000&@57
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@3>l|i|n|e|{|1| |+| |1|}| +0#0000000&@57
+||+0#0000e05#a8a8a8255| | +0#e000e06#ffffff0@1|E|N|D| +0#0000000&@67
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |e|n|d| |m|a|r|k|e|r| |m|u|s|t| |n|o|t| |b|e| |f|o|l@1|o|w|e|d| |b|y| |w|h|i|t|e|s|p|a|c|e| +0#0000000&@25
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |a|s@1|e|r|t|_|e|q|u|a|l|(|f|o@1|,| |[|"|E|N|D| |"|]|)| +0#0000000&@43
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |E|N|D| +0#0000000&@57
+||+0#0000e05#a8a8a8255| |E+0#e000002#ffffff0|N|D| | +0#0000000&@68
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |a|s@1|e|r|t|_|e|q|u|a|l|(|f|o@1|,| |[|"| |E|N|D| |"|]|)| +0#0000000&@42
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |E|N|D| +0#0000000&@57
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0|E|N|D| | +0#0000000&@67
+@57|9|1|,|5| @9|8|7|%| 
diff --git a/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_06.dump b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_06.dump
new file mode 100644
index 0000000..e3c4ca4
--- /dev/null
+++ b/runtime/syntax/testdir/dumps/vim_ex_let_heredoc_06.dump
@@ -0,0 +1,20 @@
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0|E|N|D| | +0#0000000&@67
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |a|s@1|e|r|t|_|e|q|u|a|l|(|f|o@1|,| |[|"|E|N|D| |"|]|)| +0#0000000&@43
+|-+0#0000e05#a8a8a8255| |l+0#af5f00255#ffffff0|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@52
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@1>E|N|D| | +0#0000000&@66
+||+0#0000e05#a8a8a8255| |E+0#e000e06#ffffff0|N|D| +0#0000000&@69
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+| +0#0000e05#a8a8a8255@1|"+0&#ffffff0| |a|s@1|e|r|t|_|e|q|u|a|l|(|f|o@1|,| |[|"|E|N|D| |"|]|)| +0#0000000&@43
+|-+0#0000e05#a8a8a8255| | +0#0000000#ffffff0@1|l+0#af5f00255&|e|t| +0#0000000&|f+0#00e0e07&|o@1| +0#0000000&|=+0#e000e06&|<@1| |t|r|i|m| |E|N|D| +0#0000000&@50
+||+0#0000e05#a8a8a8255| | +0#e000002#ffffff0@3|E|N|D| | +0#0000000&@64
+||+0#0000e05#a8a8a8255| | +0#e000e06#ffffff0@1|E|N|D| +0#0000000&@67
+| +0#0000e05#a8a8a8255@1| +0#0000000#ffffff0@72
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+| +0#0000000&@56|1|0|9|,|3| @8|B|o|t| 
diff --git a/runtime/syntax/testdir/input/vim_ex_def_fold.vim b/runtime/syntax/testdir/input/vim_ex_def_fold.vim
index d85f273..60b1151 100644
--- a/runtime/syntax/testdir/input/vim_ex_def_fold.vim
+++ b/runtime/syntax/testdir/input/vim_ex_def_fold.vim
@@ -120,7 +120,7 @@
 enddef
 
 def Foo()
-  let x =<< END
+  var x =<< trim END
     endfunction
   END
 enddef
diff --git a/runtime/syntax/testdir/input/vim_ex_function_fold.vim b/runtime/syntax/testdir/input/vim_ex_function_fold.vim
index dd260ca..fa7edbb 100644
--- a/runtime/syntax/testdir/input/vim_ex_function_fold.vim
+++ b/runtime/syntax/testdir/input/vim_ex_function_fold.vim
@@ -193,10 +193,9 @@
 endfunction
 
 function Foo()
-  let x =<< END
+  let x =<< trim END
     endfunction
   END
-
 endfunction
 
 function Foo()
diff --git a/runtime/syntax/testdir/input/vim_ex_let_heredoc.vim b/runtime/syntax/testdir/input/vim_ex_let_heredoc.vim
new file mode 100644
index 0000000..da9adff
--- /dev/null
+++ b/runtime/syntax/testdir/input/vim_ex_let_heredoc.vim
@@ -0,0 +1,116 @@
+" Vim :let heredoc command
+" VIM_TEST_SETUP let g:vimsyn_folding = "h"
+" VIM_TEST_SETUP setl fdc=2 fdl=99 fdm=syntax
+
+
+let foo =<< END
+line1
+line2
+END
+
+  let foo =<< END
+line1
+line2
+END
+
+let foo =<< trim END
+  line1
+  line2
+END
+
+  let foo =<< trim END
+    line1
+    line2
+  END
+
+
+" interpolation
+
+let foo =<< eval END
+line{1 + 0}
+line{1 + 1}
+END
+
+  let foo =<< eval END
+line{1 + 0}
+line{1 + 1}
+END
+
+let foo =<< trim eval END
+  line{1 + 0}
+  line{1 + 1}
+END
+
+  let foo =<< trim eval END
+    line{1 + 0}
+    line{1 + 1}
+  END
+
+" no interpolation (escaped { and })
+
+let foo =<< eval END
+line{{1 + 0}}
+line{{1 + 1}}
+END
+
+  let foo =<< eval END
+line{{1 + 0}}
+line{{1 + 1}}
+END
+
+let foo =<< trim eval END
+  line{{1 + 0}}
+  line{{1 + 1}}
+END
+
+  let foo =<< trim eval END
+    line{{1 + 0}}
+    line{{1 + 1}}
+  END
+
+
+" no interpolation
+
+let foo =<< END
+line{1 + 0}
+line{1 + 1}
+END
+
+  let foo =<< END
+line{1 + 0}
+line{1 + 1}
+END
+
+let foo =<< trim END
+  line{1 + 0}
+  line{1 + 1}
+END
+
+  let foo =<< trim END
+    line{1 + 0}
+    line{1 + 1}
+  END
+
+
+" end marker must not be followed by whitespace
+
+" assert_equal(foo, ["END "])
+let foo =<< END
+END 
+END
+
+" assert_equal(foo, [" END "])
+let foo =<< END
+ END 
+END
+
+" assert_equal(foo, ["END "])
+let foo =<< trim END
+  END 
+END
+
+" assert_equal(foo, ["END "])
+  let foo =<< trim END
+    END 
+  END
+
diff --git a/runtime/syntax/vim.vim b/runtime/syntax/vim.vim
index 8492463..441f74f 100644
--- a/runtime/syntax/vim.vim
+++ b/runtime/syntax/vim.vim
@@ -3,7 +3,7 @@
 " Maintainer:	   Hirohito Higashi <h.east.727 ATMARK gmail.com>
 "	   Doug Kearns <dougkearns@gmail.com>
 " URL:	   https://github.com/vim-jp/syntax-vim-ex
-" Last Change:	   2024 Jul 23
+" Last Change:	   2024 Aug 16
 " Former Maintainer: Charles E. Campbell
 
 " DO NOT CHANGE DIRECTLY.
@@ -480,11 +480,12 @@
 syn match	vimEscape	contained	"\\<" contains=vimNotation
 syn match	vimEscape	contained	"\\<\*[^>]*>\=>"
 
-syn region	vimString	oneline start=+$'+ skip=+''+ end=+'+ contains=vimStringInterpolationBrace,vimStringInterpolationExpr
-syn region	vimString	oneline start=+$"+ end=+"+ contains=@vimStringGroup,vimStringInterpolationBrace,vimStringInterpolationExpr
+syn region	vimString	oneline start=+$'+ skip=+''+ end=+'+ contains=@vimStringInterpolation
+syn region	vimString	oneline start=+$"+ end=+"+ contains=@vimStringGroup,@vimStringInterpolation
 syn region	vimStringInterpolationExpr  oneline contained matchgroup=vimSep start=+{+ end=+}+ contains=@vimExprList
 syn match	vimStringInterpolationBrace contained "{{"
 syn match	vimStringInterpolationBrace contained "}}"
+syn cluster	vimStringInterpolation contains=vimStringInterpolationExpr,vimStringInterpolationBrace
 
 " Substitutions: {{{2
 " =============
@@ -564,7 +565,13 @@
 syn match	vimUnletBang	contained	"!"	skipwhite nextgroup=vimUnletVars
 syn region	vimUnletVars	contained	start="$\I\|\h" skip="\n\s*\\" end="$" end="|" contains=vimVar,vimEnvvar,vimContinue,vimString,vimNumber
 
-VimFoldh syn region vimLetHereDoc	matchgroup=vimLetHereDocStart start='=<<\s*\%(trim\s\+\%(eval\s\+\)\=\|eval\s\+\%(trim\s\+\)\=\)\=\z(\L\S*\)' matchgroup=vimLetHereDocStop end='^\s*\z1\s*$' extend
+" Note: This incorrectly matches end markers with leading whitespace even if
+"       "trim" was not specified.  Matching :let indent for "trim" indented
+"       end markers would require a contained :let that cannot be restricted
+"       to the start pattern.  A common internal testing use of heredocs is to
+"       specify code blocks where :let commonly appears in the heredoc text.
+VimFoldh syn region vimLetHereDoc	matchgroup=vimLetHereDocStart start='=<<\s*\%(trim\s\+\)\=\z(\L\S*\)'			matchgroup=vimLetHereDocStop end='^\s*\z1$' extend
+VimFoldh syn region vimLetHereDoc	matchgroup=vimLetHereDocStart start='=<<\s*\%(\%(trim\s\+\)\=eval\s\+\|eval\s\+\%(trim\s\+\)\=\)\z(\L\S*\)' matchgroup=vimLetHereDocStop end='^\s*\z1$' contains=@vimStringInterpolation extend
 
 Vim9 syn keyword	vim9Const	const	skipwhite nextgroup=vim9Variable,vim9VariableList
 Vim9 syn keyword	vim9Final	final	skipwhite nextgroup=vim9Variable,vim9VariableList