diff --git a/build_tools/list_committers_since.fish b/build_tools/list_committers_since.fish
index 25d2e4969..40df26b40 100755
--- a/build_tools/list_committers_since.fish
+++ b/build_tools/list_committers_since.fish
@@ -12,8 +12,8 @@ if not contains -- $TAG (git tag)
     exit 1
 end
 
-set committers_to_tag (mktemp)
-set committers_from_tag (mktemp)
+set -l committers_to_tag (mktemp)
+set -l committers_from_tag (mktemp)
 
 # You might think it would be better to case-insensitively sort/compare the names
 # to produce a more natural-looking list.
diff --git a/share/functions/__fish_append.fish b/share/functions/__fish_append.fish
index d40163cab..ea6332344 100644
--- a/share/functions/__fish_append.fish
+++ b/share/functions/__fish_append.fish
@@ -1,6 +1,6 @@
 function __fish_append -d "Internal completion function for appending string to the commandline" --argument sep
     set -e argv[1]
-    set str (commandline -tc | string replace -rf "(.*$sep)[^$sep]*" '$1' | string replace -r -- '--.*=' '')
+    set -l str (commandline -tc | string replace -rf "(.*$sep)[^$sep]*" '$1' | string replace -r -- '--.*=' '')
     printf "%s\n" "$str"$argv
 end
 
diff --git a/share/functions/__fish_complete_mount_opts.fish b/share/functions/__fish_complete_mount_opts.fish
index 378262d8e..2e082a5b4 100644
--- a/share/functions/__fish_complete_mount_opts.fish
+++ b/share/functions/__fish_complete_mount_opts.fish
@@ -1,7 +1,7 @@
 function __fish_print_user_ids
     if command -sq getent
         for line in (getent passwd)
-            set v (string split : -- $line)
+            set -l v (string split : -- $line)
             printf "%s\t%s\n" $v[3] $v[1]
         end
     end
@@ -10,7 +10,7 @@ end
 function __fish_print_group_ids
     if command -sq getent
         for line in (getent group)
-            set v (string split : -- $line)
+            set -l v (string split : -- $line)
             printf "%s\t%s\n" $v[3] $v[1]
         end
     end
diff --git a/share/functions/__fish_complete_subcommand.fish b/share/functions/__fish_complete_subcommand.fish
index c0dfaefe2..020a74efd 100644
--- a/share/functions/__fish_complete_subcommand.fish
+++ b/share/functions/__fish_complete_subcommand.fish
@@ -25,7 +25,7 @@ function __fish_complete_subcommand -d "Complete subcommand" --no-scope-shadowin
     set -l options_with_param $argv
 
     if not string length -q -- $subcommand
-        set cmd (commandline -cop) (commandline -ct)
+        set -l cmd (commandline -cop) (commandline -ct)
         while set -q cmd[1]
             set -l token $cmd[1]
             set -e cmd[1]
diff --git a/share/functions/__fish_list_current_token.fish b/share/functions/__fish_list_current_token.fish
index 3fd7f61e8..2ebfb73e5 100644
--- a/share/functions/__fish_list_current_token.fish
+++ b/share/functions/__fish_list_current_token.fish
@@ -2,12 +2,12 @@
 # of the directory under the cursor.
 
 function __fish_list_current_token -d "List contents of token under the cursor if it is a directory, otherwise list the contents of the current directory"
-    set val (eval echo (commandline -t))
+    set -l val (eval echo (commandline -t))
     printf "\n"
     if test -d $val
         ls $val
     else
-        set dir (dirname -- $val)
+        set -l dir (dirname -- $val)
         if test $dir != . -a -d $dir
             ls $dir
         else
diff --git a/share/functions/__fish_npm_helper.fish b/share/functions/__fish_npm_helper.fish
index 146375da7..784c39608 100644
--- a/share/functions/__fish_npm_helper.fish
+++ b/share/functions/__fish_npm_helper.fish
@@ -38,7 +38,7 @@ function __yarn_filtered_list_packages
 end
 
 function __yarn_find_package_json
-    set parents (__fish_parent_directories (pwd -P))
+    set -l parents (__fish_parent_directories (pwd -P))
 
     for p in $parents
         if test -f "$p/package.json"
diff --git a/share/functions/__fish_print_packages.fish b/share/functions/__fish_print_packages.fish
index f4f0e3c01..07e7dfcc1 100644
--- a/share/functions/__fish_print_packages.fish
+++ b/share/functions/__fish_print_packages.fish
@@ -113,8 +113,8 @@ function __fish_print_packages
         set -l cache_file $xdg_cache_home/.yum-cache.$USER
         if test -f $cache_file
             cat $cache_file
-            set age (math (date +%s) - (stat -c '%Y' $cache_file))
-            set max_age 21600
+            set -l age (math (date +%s) - (stat -c '%Y' $cache_file))
+            set -l max_age 21600
             if test $age -lt $max_age
                 return
             end
@@ -135,8 +135,8 @@ function __fish_print_packages
         set -l cache_file $xdg_cache_home/.rpm-cache.$USER
         if test -f $cache_file
             cat $cache_file
-            set age (math (date +%s) - (stat -c '%Y' $cache_file))
-            set max_age 250
+            set -l age (math (date +%s) - (stat -c '%Y' $cache_file))
+            set -l max_age 250
             if test $age -lt $max_age
                 return
             end
@@ -158,8 +158,8 @@ function __fish_print_packages
             set -l cache_file $xdg_cache_home/.eopkg-installed-cache.$USER
             if test -f $cache_file
                 cat $cache_file
-                set age (math (date +%s) - (stat -c '%Y' $cache_file))
-                set max_age 500
+                set -l age (math (date +%s) - (stat -c '%Y' $cache_file))
+                set -l max_age 500
                 if test $age -lt $max_age
                     return
                 end
@@ -172,8 +172,8 @@ function __fish_print_packages
             set -l cache_file $xdg_cache_home/.eopkg-available-cache.$USER
             if test -f $cache_file
                 cat $cache_file
-                set age (math (date +%s) - (stat -c '%Y' $cache_file))
-                set max_age 500
+                set -l age (math (date +%s) - (stat -c '%Y' $cache_file))
+                set -l max_age 500
                 if test $age -lt $max_age
                     return
                 end
diff --git a/share/functions/__fish_seen_argument.fish b/share/functions/__fish_seen_argument.fish
index 2f8704387..6c23d23c2 100644
--- a/share/functions/__fish_seen_argument.fish
+++ b/share/functions/__fish_seen_argument.fish
@@ -1,7 +1,7 @@
 function __fish_seen_argument
     argparse 's/short=+' 'o/old=+' 'l/long=+' -- $argv
 
-    set cmd (commandline -co)
+    set -l cmd (commandline -co)
     set -e cmd[1]
     for t in $cmd
         for s in $_flag_s
diff --git a/share/functions/realpath.fish b/share/functions/realpath.fish
index 1bb0a8f5e..888bb1665 100644
--- a/share/functions/realpath.fish
+++ b/share/functions/realpath.fish
@@ -35,7 +35,7 @@ function realpath -d "return an absolute path without symlinks"
 
     # We don't implement any of the other flags so if any are set it's an error.
     if string match -q '_flag_*' -- (set -l)
-        set flags (set -l | string replace --filter _flag_ '')
+        set -l flags (set -l | string replace --filter _flag_ '')
         printf (_ "%s: These flags are not allowed by fish realpath: '%s'") realpath "$flags" >&2
         echo >&2
         __fish_print_help realpath
diff --git a/share/functions/trap.fish b/share/functions/trap.fish
index c710ce97f..a9b97dffb 100644
--- a/share/functions/trap.fish
+++ b/share/functions/trap.fish
@@ -65,7 +65,7 @@ function trap -d 'Perform an action when the shell receives a signal'
 
             for i in $argv
                 set -l sig (__trap_translate_signal $i)
-                set sw (__trap_switch $sig)
+                set -l sw (__trap_switch $sig)
 
                 if test -n "$sig"
                     echo "function __trap_handler_$sig $sw; $cmd; end" | source
diff --git a/share/functions/up-or-search.fish b/share/functions/up-or-search.fish
index e0e64f6dd..3d7ae1417 100644
--- a/share/functions/up-or-search.fish
+++ b/share/functions/up-or-search.fish
@@ -14,7 +14,7 @@ function up-or-search -d "Depending on cursor position and current mode, either
     # We are not already in search mode.
     # If we are on the top line, start search mode,
     # otherwise move up
-    set lineno (commandline -L)
+    set -l lineno (commandline -L)
 
     switch $lineno
         case 1