diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 5848471..33c9786 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -17,7 +17,9 @@ jobs:
       fail-fast: false
       matrix:
         cip_tag:
-          - "5.41"
+          - "5.45"
+          - "5.44"
+          - "5.42"
           - "5.40"
           - "5.38"
           - "5.36"
@@ -40,7 +42,7 @@ jobs:
       CIP_TAG: ${{ matrix.cip_tag }}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v7
 
       - name: Bootstrap CIP
         run: |
@@ -53,7 +55,7 @@ jobs:
           cip cache-key
 
       - name: Cache CPAN modules
-        uses: actions/cache@v2
+        uses: actions/cache@v6
         with:
           path: ~/.cip
           key: ${{ runner.os }}-build-${{ steps.cache-key.outputs.key }}
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index d2b8134..36b6276 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -23,7 +23,7 @@ jobs:
       fail-fast: false
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v7
 
       - name: Set up Perl
         run: |
@@ -40,7 +40,7 @@ jobs:
           ls -l perlversion.txt
 
       - name: Cache CPAN modules
-        uses: actions/cache@v1
+        uses: actions/cache@v6
         with:
           path: ~/perl5
           key: ${{ runner.os }}-build-${{ hashFiles('perlversion.txt') }}
diff --git a/.github/workflows/msys2-mingw.yml b/.github/workflows/msys2-mingw.yml
index 2743442..6f203a0 100644
--- a/.github/workflows/msys2-mingw.yml
+++ b/.github/workflows/msys2-mingw.yml
@@ -34,7 +34,7 @@ jobs:
           git config --global core.eol lf
         shell: powershell
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v7
 
       - name: Set up Perl
         uses: msys2/setup-msys2@v2
@@ -57,7 +57,7 @@ jobs:
           ls perlversion.txt
 
       - name: Cache CPAN modules
-        uses: actions/cache@v1
+        uses: actions/cache@v6
         with:
           path: c:\cx
           key: ${{ runner.os }}-build-msys2-${{ hashFiles('perlversion.txt') }}
diff --git a/.github/workflows/static.yml b/.github/workflows/static.yml
index cba7de1..a5ed5f1 100644
--- a/.github/workflows/static.yml
+++ b/.github/workflows/static.yml
@@ -17,7 +17,7 @@ jobs:
       CIP_TAG: static
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v7
 
       - name: Bootstrap CIP
         run: |
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 913e2d0..16cbd07 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -28,7 +28,7 @@ jobs:
           git config --global core.autocrlf false
           git config --global core.eol lf
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v7
 
       - name: Set up Perl
         run: |
@@ -43,7 +43,7 @@ jobs:
           perl -V > perlversion.txt
 
       - name: Cache CPAN modules
-        uses: actions/cache@v1
+        uses: actions/cache@v6
         env:
           cache-name: cache-cpan-modules
         with:
diff --git a/Changes b/Changes
index 9497d69..5477db3 100644
--- a/Changes
+++ b/Changes
@@ -1,6 +1,8 @@
 Revision history for {{$dist->name}}
 
 {{$NEXT}}
+  - Clarify that "MacOS" in comments and docs refers to the classic,
+    pre-OS X environment (now called OS9 for short) (gh#43, gh#47)
 
 1.27      2021-05-07 04:54:31 -0600
   - Production release identical to 1.26_01
diff --git a/README.md b/README.md
index bb3420a..f192099 100644
--- a/README.md
+++ b/README.md
@@ -90,6 +90,19 @@ certain it has ever been tested on VMS.  If this platform is important to you
 and you can help me verify and or support it on that platform please contact
 me.
 
+### OS9
+
+Prior to Mac OS X, "classic" Mac OS (System 7, 8 and 9) used `$^O` value
+`MacOS` and had a very different filesystem and process model than the
+Darwin-based macOS of today.  Throughout this document and in the source
+code, `OS9` is used as a shorthand to refer to this classic, pre-OS X
+environment (covering Mac OS 7 and 8 as well as 9).  Modern Apple macOS is
+Unix-like and is covered by the ["Linux, \*BSD and other UNIXes"](#linux-bsd-and-other-unixes) section
+above instead.
+
+As of 2015 the current maintainer does not test on OS9, and this platform
+is essentially unmaintained.
+
 # FUNCTIONS
 
 ## which
diff --git a/author.yml b/author.yml
index aa1c86e..71ef27b 100644
--- a/author.yml
+++ b/author.yml
@@ -9,6 +9,7 @@ pod_spelling_system:
     - DocSet
     - Einar
     - Ellefsen
+    - macOS
     - OS2
     - Stas
     - Win32
diff --git a/lib/File/Which.pm b/lib/File/Which.pm
index 915f8a3..544f078 100644
--- a/lib/File/Which.pm
+++ b/lib/File/Which.pm
@@ -94,6 +94,19 @@ certain it has ever been tested on VMS.  If this platform is important to you
 and you can help me verify and or support it on that platform please contact
 me.
 
+=head3 OS9
+
+Prior to Mac OS X, "classic" Mac OS (System 7, 8 and 9) used C<$^O> value
+C<MacOS> and had a very different filesystem and process model than the
+Darwin-based macOS of today.  Throughout this document and in the source
+code, C<OS9> is used as a shorthand to refer to this classic, pre-OS X
+environment (covering Mac OS 7 and 8 as well as 9).  Modern Apple macOS is
+Unix-like and is covered by the L</"Linux, *BSD and other UNIXes"> section
+above instead.
+
+As of 2015 the current maintainer does not test on OS9, and this platform
+is essentially unmaintained.
+
 =cut
 
 our @EXPORT    = 'which';
@@ -217,7 +230,7 @@ sub which {
         # Executable, normal case
         -x _
         or (
-          # MacOS doesn't mark as executable so we check -e
+          # OS9 (classic Mac OS) doesn't mark files as executable, so we check -e instead
           IS_MAC  ## no critic (ValuesAndExpressions::ProhibitMixedBooleanOperators)
           ||
           (
diff --git a/t/file_which.t b/t/file_which.t
index d398249..3502e19 100644
--- a/t/file_which.t
+++ b/t/file_which.t
@@ -76,7 +76,7 @@ unless (File::Which::IS_VMS or File::Which::IS_MAC or File::Which::IS_WIN ) {
     );
   }
 
-  # Make sure that .\ stuff works on DOSish, VMS, MacOS (. is in PATH implicitly).
+  # Make sure that .\ stuff works on DOSish, VMS, OS9 (classic Mac OS) (. is in PATH implicitly).
   SKIP: {
     unless ( File::Which::IS_WIN or File::Which::IS_VMS ) {
       skip("Not on a DOS or VMS filesystem", 1);