diff --git a/sh/v_domap b/sh/v_domap
new file mode 100644
index 0000000..085d55a
--- /dev/null
+++ b/sh/v_domap
@@ -0,0 +1,25 @@
+#!/usr/bin/env sh
+# YES_ZSH
+# YES_BASH
+# YES_DASH
+# YES_ASH
+
+v_domap() {
+    argc $# -eq 1 "$0" || return
+    # TODO: sanity-check on characters of the variable name.
+    local _k_="$1" _v_= _new_= _next_= _i_= _o_=
+    eval "_v_=\"\$$_k_\""
+    while [ -n "$_v_" ]; do
+        _next_="${_v_#[! ]}"
+        [ "$_next_" != "$_v_" ] || _next_="${_v_# }"
+        _i_="${_v_%"$_next_"}"; _v_="$_next_"
+        map
+        _new_="$_new_$_o_"
+        #printf 'new: %s\n' "$_new_"
+    done
+    eval "$_k_=\"\$_new_\""
+}
+
+[ -n "${preload+-}" ] || . ~/sh/preload || exit 2
+eval ${preload:-preload} argc
+[ -n "${preload+-}" ] || v_domap "$@"
diff --git a/sh/v_lower b/sh/v_lower
new file mode 100644
index 0000000..850200a
--- /dev/null
+++ b/sh/v_lower
@@ -0,0 +1,22 @@
+#!/usr/bin/env sh
+# YES_ZSH
+# YES_BASH
+# YES_DASH
+# YES_ASH
+
+v_lower() { ### @- transform the contents of a variable to lowercase.
+    argc $# -eq 1 "$0" || return
+    map() {
+        case "$_i_" in
+        (A) _o_=a;; (B) _o_=b;; (C) _o_=c;; (D) _o_=d;; (E) _o_=e;; (F) _o_=f;; (G) _o_=g;;
+        (H) _o_=h;; (I) _o_=i;; (J) _o_=j;; (K) _o_=k;; (L) _o_=l;; (M) _o_=m;; (N) _o_=n;;
+        (O) _o_=o;; (P) _o_=p;; (Q) _o_=q;; (R) _o_=r;; (S) _o_=s;; (T) _o_=t;; (U) _o_=u;;
+        (V) _o_=v;; (W) _o_=w;; (X) _o_=x;; (Y) _o_=y;; (Z) _o_=z;; (*) _o_="$_i_";;
+        esac
+    }
+    v_domap "$1"
+}
+
+[ -n "${preload+-}" ] || . ~/sh/preload || exit 2
+eval ${preload:-preload} argc v_domap
+[ -n "${preload+-}" ] || v_lower "$@"
diff --git a/sh/v_upper b/sh/v_upper
new file mode 100644
index 0000000..07d5b0a
--- /dev/null
+++ b/sh/v_upper
@@ -0,0 +1,22 @@
+#!/usr/bin/env sh
+# YES_ZSH
+# YES_BASH
+# YES_DASH
+# YES_ASH
+
+v_upper() { ### @- transform the contents of a variable to uppercase.
+    argc $# -eq 1 "$0" || return
+    map() {
+        case "$_i_" in
+        (a) _o_=A;; (b) _o_=B;; (c) _o_=C;; (d) _o_=D;; (e) _o_=E;; (f) _o_=F;; (g) _o_=G;;
+        (h) _o_=H;; (i) _o_=I;; (j) _o_=J;; (k) _o_=K;; (l) _o_=L;; (m) _o_=M;; (n) _o_=N;;
+        (o) _o_=O;; (p) _o_=P;; (q) _o_=Q;; (r) _o_=R;; (s) _o_=S;; (t) _o_=T;; (u) _o_=U;;
+        (v) _o_=V;; (w) _o_=W;; (x) _o_=X;; (y) _o_=Y;; (z) _o_=Z;; (*) _o_="$_i_";;
+        esac
+    }
+    v_domap "$1"
+}
+
+[ -n "${preload+-}" ] || . ~/sh/preload || exit 2
+eval ${preload:-preload} argc v_domap
+[ -n "${preload+-}" ] || v_upper "$@"