Bash, script qui vérifie le soft

J'ai un script sur bash :

s=0
 if [ -f /usr/bin/curl ] && [ -x /usr/bin/curl ] ; then
    echo  "Utility ...... curl [ ok ]"
    else
    echo  "Utility ...... curl [fail]"
    s=1
 fi
 if [ -f "/bin/grep" ] && [ -x "/bin/grep" ] ; then
    echo  "Utility ...... grep [ ok ]"
    else
    echo  "Utility ...... grep [fail]"
    s=1
 fi
 if [ -f "/usr/bin/expr" ] && [ -x "/usr/bin/expr" ] ; then
    echo  "Utility ...... expr [ ok ]"
    else
    echo  "Utility ...... expr [fail]"
    s=1
 fi
 if [ -f "/bin/sed" ] && [ -x "/bin/sed" ] ; then
    echo  "Utility ...... sed  [ ok ]"
    else
    echo  "Utility ...... sed  [fail]"
    s=1
 fi
 if [ $s -eq 0 ]; then
    echo  "All seems to be good. Let's play."
 else
    echo  "Please install requirement util! "
 fi

Je veux écrire sans /usr/bin ou /bin. Je veux écrire une seule variable :

$ENV/curl

Et d'autres ...
Comment procéder.