diff --git a/autoload/latex/change.vim b/autoload/latex/change.vim
index 98ef420..6775fb3 100644
--- a/autoload/latex/change.vim
+++ b/autoload/latex/change.vim
@@ -7,6 +7,18 @@ function! latex#change#init(initialized)
   endif
 endfunction
 
+" {{{1 latex#change#delim
+function! latex#change#delim(open, close)
+  let [d1, l1, c1, d2, l2, c2] = latex#util#get_delim(1)
+
+  let line = getline(l1)
+  let line = strpart(line, 0, c1 - 1) . a:open  . strpart(line, c1 + len(d1))
+  call setline(l1, line)
+  let line = getline(l2)
+  let line = strpart(line, 0, c2 - 1) . a:close . strpart(line, c2 + len(d2))
+  call setline(l2, line)
+endfunction
+
 " {{{1 latex#change#env
 function! latex#change#env(new_env)
   let [env, l1, c1, l2, c2] = latex#util#get_env(1)
diff --git a/autoload/latex/util.vim b/autoload/latex/util.vim
index 19dcde7..2b60c30 100644
--- a/autoload/latex/util.vim
+++ b/autoload/latex/util.vim
@@ -86,11 +86,64 @@ function! latex#util#get_env(...)
   "         if with_pos is not given
   " - [environment, lnum_begin, cnum_begin, lnum_end, cnum_end]
   "         if with_pos is nonzero
-  if a:0 > 0
-    let with_pos = a:1
-  else
-    let with_pos = 0
+  let with_pos = a:0 > 0 ? a:1 : 0
+
+  let begin_pat = '\C\\begin\_\s*{[^}]*}\|\\\@<!\\\[\|\\\@<!\\('
+  let end_pat = '\C\\end\_\s*{[^}]*}\|\\\@<!\\\]\|\\\@<!\\)'
+  let saved_pos = getpos('.')
+
+  " move to the left until on a backslash
+  let [bufnum, lnum, cnum, off] = getpos('.')
+  let line = getline(lnum)
+  while cnum > 1 && line[cnum - 1] != '\'
+    let cnum -= 1
+  endwhile
+  call cursor(lnum, cnum)
+
+  " match begin/end pairs but skip comments
+  let flags = 'bnW'
+  if strpart(getline('.'), col('.') - 1) =~ '^\%(' . begin_pat . '\)'
+    let flags .= 'c'
   endif
+  let [lnum1, cnum1] = searchpairpos(begin_pat, '', end_pat, flags,
+        \ 'latex#util#in_comment()')
+
+  let env = ''
+
+  if lnum1
+    let line = strpart(getline(lnum1), cnum1 - 1)
+
+    if empty(env)
+      let env = matchstr(line, '^\C\\begin\_\s*{\zs[^}]*\ze}')
+    endif
+    if empty(env)
+      let env = matchstr(line, '^\\\[')
+    endif
+    if empty(env)
+      let env = matchstr(line, '^\\(')
+    endif
+  endif
+
+  if with_pos == 1
+    let flags = 'nW'
+    if !(lnum1 == lnum && cnum1 == cnum)
+      let flags .= 'c'
+    endif
+
+    let [lnum2, cnum2] = searchpairpos(begin_pat, '', end_pat, flags,
+          \ 'latex#util#in_comment()')
+
+    call setpos('.', saved_pos)
+    return [env, lnum1, cnum1, lnum2, cnum2]
+  else
+    call setpos('.', saved_pos)
+    return env
+  endif
+endfunction
+
+" {{{1 latex#util#get_delim
+function! latex#util#get_delim(...)
+  let with_pos = a:0 > 0 ? a:1 : 0
 
   let begin_pat = '\C\\begin\_\s*{[^}]*}\|\\\@<!\\\[\|\\\@<!\\('
   let end_pat = '\C\\end\_\s*{[^}]*}\|\\\@<!\\\]\|\\\@<!\\)'