rc/sh/v_domap

#!/usr/bin/env sh
# compat: +ash +bash +dash +zsh

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_#?}"
        _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 "$@"