diff --git a/extras/vpnsetup-debian-7-workaround.sh b/extras/vpnsetup-debian-7-workaround.sh
index 6230ce8..21fcae7 100644
--- a/extras/vpnsetup-debian-7-workaround.sh
+++ b/extras/vpnsetup-debian-7-workaround.sh
@@ -22,7 +22,7 @@
 
 export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
-exiterr() { echo "Error: ${1}" >&2; exit 1; }
+exiterr() { echo "Error: $1" >&2; exit 1; }
 
 if [ "$(sed 's/\..*//' /etc/debian_version 2>/dev/null)" != "7" ]; then
   exiterr "This script only supports Debian 7 (Wheezy)."
diff --git a/extras/vpnupgrade.sh b/extras/vpnupgrade.sh
index c3d37c5..d73515b 100644
--- a/extras/vpnupgrade.sh
+++ b/extras/vpnupgrade.sh
@@ -13,11 +13,11 @@
 # Check https://libreswan.org for the latest version
 swan_ver=3.18
 
-### Do not edit below this line ###
+### DO NOT edit below this line ###
 
 export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
-exiterr()  { echo "Error: ${1}" >&2; exit 1; }
+exiterr()  { echo "Error: $1" >&2; exit 1; }
 exiterr2() { echo "Error: 'apt-get install' failed." >&2; exit 1; }
 
 os_type="$(lsb_release -si 2>/dev/null)"
@@ -37,13 +37,11 @@ if [ -z "$swan_ver" ]; then
   exiterr "Libreswan version 'swan_ver' not specified."
 fi
 
-/usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "Libreswan"
-if [ "$?" != "0" ]; then
+if ! /usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "Libreswan"; then
   exiterr "This script requires Libreswan already installed."
 fi
 
-/usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "$swan_ver"
-if [ "$?" = "0" ]; then
+if /usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "$swan_ver"; then
   echo "You already have Libreswan version $swan_ver installed! "
   echo "If you continue, the same version will be re-installed."
   echo
diff --git a/extras/vpnupgrade_centos.sh b/extras/vpnupgrade_centos.sh
index 8cdbafc..98eabbf 100644
--- a/extras/vpnupgrade_centos.sh
+++ b/extras/vpnupgrade_centos.sh
@@ -13,11 +13,11 @@
 # Check https://libreswan.org for the latest version
 swan_ver=3.18
 
-### Do not edit below this line ###
+### DO NOT edit below this line ###
 
 export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
-exiterr()  { echo "Error: ${1}" >&2; exit 1; }
+exiterr()  { echo "Error: $1" >&2; exit 1; }
 exiterr2() { echo "Error: 'yum install' failed." >&2; exit 1; }
 
 if ! grep -qs -e "release 6" -e "release 7" /etc/redhat-release; then
@@ -36,13 +36,11 @@ if [ -z "$swan_ver" ]; then
   exiterr "Libreswan version 'swan_ver' not specified."
 fi
 
-/usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "Libreswan"
-if [ "$?" != "0" ]; then
+if ! /usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "Libreswan"; then
   exiterr "This script requires Libreswan already installed."
 fi
 
-/usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "$swan_ver"
-if [ "$?" = "0" ]; then
+if /usr/local/sbin/ipsec --version 2>/dev/null | grep -qs "$swan_ver"; then
   echo "You already have Libreswan version $swan_ver installed! "
   echo "If you continue, the same version will be re-installed."
   echo
diff --git a/vpnsetup.sh b/vpnsetup.sh
index 7deed8e..799c5aa 100755
--- a/vpnsetup.sh
+++ b/vpnsetup.sh
@@ -36,12 +36,13 @@ YOUR_PASSWORD=''
 export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 SYS_DT="$(date +%Y-%m-%d-%H:%M:%S)"; export SYS_DT
 
-exiterr()  { echo "Error: ${1}" >&2; exit 1; }
+exiterr()  { echo "Error: $1" >&2; exit 1; }
 exiterr2() { echo "Error: 'apt-get install' failed." >&2; exit 1; }
-conf_bk() { /bin/cp -f "${1}" "${1}.old-$SYS_DT" 2>/dev/null; }
+conf_bk() { /bin/cp -f "$1" "$1.old-$SYS_DT" 2>/dev/null; }
+
 check_ip() {
   IP_REGEX="^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$"
-  printf %s "${1}" | tr -d '\n' | grep -Eq "$IP_REGEX"
+  printf %s "$1" | tr -d '\n' | grep -Eq "$IP_REGEX"
 }
 
 os_type="$(lsb_release -si 2>/dev/null)"
@@ -335,9 +336,9 @@ fi
 # Check if IPTables rules need updating
 ipt_flag=0
 IPT_FILE="/etc/iptables.rules"
-if ! grep -qs "hwdsl2 VPN script" "$IPT_FILE" || \
-   ! iptables -t nat -C POSTROUTING -s 192.168.42.0/24 -o "$NET_IFS" -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null || \
-   ! iptables -t nat -C POSTROUTING -s 192.168.43.0/24 -o "$NET_IFS" -m policy --dir out --pol none -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null; then
+if ! grep -qs "hwdsl2 VPN script" "$IPT_FILE" \
+   || ! iptables -t nat -C POSTROUTING -s 192.168.42.0/24 -o "$NET_IFS" -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null \
+   || ! iptables -t nat -C POSTROUTING -s 192.168.43.0/24 -o "$NET_IFS" -m policy --dir out --pol none -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null; then
   ipt_flag=1
 fi
 
diff --git a/vpnsetup_centos.sh b/vpnsetup_centos.sh
index 444af4a..59a3b55 100755
--- a/vpnsetup_centos.sh
+++ b/vpnsetup_centos.sh
@@ -36,12 +36,13 @@ YOUR_PASSWORD=''
 export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 SYS_DT="$(date +%Y-%m-%d-%H:%M:%S)"; export SYS_DT
 
-exiterr()  { echo "Error: ${1}" >&2; exit 1; }
+exiterr()  { echo "Error: $1" >&2; exit 1; }
 exiterr2() { echo "Error: 'yum install' failed." >&2; exit 1; }
-conf_bk() { /bin/cp -f "${1}" "${1}.old-$SYS_DT" 2>/dev/null; }
+conf_bk() { /bin/cp -f "$1" "$1.old-$SYS_DT" 2>/dev/null; }
+
 check_ip() {
   IP_REGEX="^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$"
-  printf %s "${1}" | tr -d '\n' | grep -Eq "$IP_REGEX"
+  printf %s "$1" | tr -d '\n' | grep -Eq "$IP_REGEX"
 }
 
 if ! grep -qs -e "release 6" -e "release 7" /etc/redhat-release; then
@@ -325,9 +326,9 @@ fi
 # Check if IPTables rules need updating
 ipt_flag=0
 IPT_FILE="/etc/sysconfig/iptables"
-if ! grep -qs "hwdsl2 VPN script" "$IPT_FILE" || \
-   ! iptables -t nat -C POSTROUTING -s 192.168.42.0/24 -o "$NET_IFS" -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null || \
-   ! iptables -t nat -C POSTROUTING -s 192.168.43.0/24 -o "$NET_IFS" -m policy --dir out --pol none -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null; then
+if ! grep -qs "hwdsl2 VPN script" "$IPT_FILE" \
+   || ! iptables -t nat -C POSTROUTING -s 192.168.42.0/24 -o "$NET_IFS" -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null \
+   || ! iptables -t nat -C POSTROUTING -s 192.168.43.0/24 -o "$NET_IFS" -m policy --dir out --pol none -j SNAT --to-source "$PRIVATE_IP" 2>/dev/null; then
   ipt_flag=1
 fi