diff --git a/README.md b/README.md
index fda4b5c..8d039d2 100644
--- a/README.md
+++ b/README.md
@@ -20,8 +20,8 @@ The build script reads `version.env` for actual version definitions.
 yum groupinstall -y "Development Tools"
 yum install -y imake rpm-build pam-devel krb5-devel zlib-devel libXt-devel libX11-devel gtk2-devel perl-IPC-Cmd
 
-# For CentOS5:
-yum install gcc44
+# For CentOS5 only:
+yum install -y gcc44
 ```
 
 ## Usage
@@ -29,19 +29,14 @@ yum install gcc44
 ### Build RPMs
 
 ```bash
-# 1. Install build requirements as listed above.
+# 1. Install build requirements listed above.
 # 2. Edit version.env file if necessary.
-
 # 3. Download source packages.
 ./pullsrc.sh
 # if any error comes up, manally download the source files into the `downloads` dir.
 
 # 4. Run the script to build RPMs. 
 ./compile.sh
-
-# For CentOS 5 
-./compile.sh el5
-# CentOS5 didn't set the variable of `${dist}`, manually run the script with argument.
 ```
 
 
@@ -54,9 +49,7 @@ if test -e /etc/ssh/sshd_config; then
 fi
 
 # Force install compiled packages.
-yum install -y coreutils
-OS_DIST="$(rpm --eval '%{?dist}'|tr -d '.')"
-[ -z "$OS_DIST" ] && OS_DIST="el5"
+OS_DIST="$(./compile GETEL | tr -d '.')"
 BASE_PATH="$PWD/$OS_DIST/RPMS/$(uname -m)"
 
 yum --disablerepo=* localinstall $BASE_PATH/openssh-*.rpm
diff --git a/compile.sh b/compile.sh
index c9bd932..7a37cc8 100755
--- a/compile.sh
+++ b/compile.sh
@@ -29,8 +29,12 @@ CHECKEXISTS() {
 }
 
 
-GUESS_DIST_BY_GLIBC() {
+GUESS_DIST() {
+        local dist=$(rpm --eval '%{?dist}' | tr -d '.')
+        [[ -n $dist ]] && echo $dist && return 0
+
 	local glibcver=$(ldd --version | head -n1 | grep -Eo '[0-9]+' | tr -d '\n')
+
 	# centos 5 uses glibc 2.5
 	[[ $glibcver -eq 25 ]] && echo 'el5' && return 0
 
@@ -40,7 +44,7 @@ GUESS_DIST_BY_GLIBC() {
 	# centos 7 uses glibc 2.17
 	[[ $glibcver -eq 217 ]] && echo 'el7' && return 0
 
-	# centos 8 uses glibc 2.28, not yet to be in a seprate dir yet
+	# centos 8 uses glibc 2.28, not yet to be in a seprate dir
 	#[[ $glibcver -eq 228 ]] && echo 'el8' && return 0
 
 	# some centos-like dists ships higher version of glibc, fallback to el7
@@ -48,33 +52,31 @@ GUESS_DIST_BY_GLIBC() {
 }
 
 if [[ -z $rpmtopdir ]]; then
-    VENDOR=$(rpm --eval '%{?_vendor}')
-    VAREL=$(rpm --eval '%{?dist}')
-    [[ -z $VAREL ]] && VAREL=".$(GUESS_DIST_BY_GLIBC)"
-
-    case $VAREL in
-        .amzn1)
+    DISTVER=$(GUESS_DIST)
+    case $DISTVER in
+        amzn1)
             rpmtopdir=amzn1
             ;;
-        .amzn2)
+        amzn2)
             rpmtopdir=amzn2
             ;;
-        .amzn2023)
+        amzn2023)
             rpmtopdir=amzn2023
             ;;
-        .el7)
+        el7)
             rpmtopdir=el7
             ;;
-        .el6)
+        el6)
             rpmtopdir=el6
             ;;
-        .el5)
+        el5)
             rpmtopdir=el5
             # on centos5, it's prefered to use gcc44
 	    rpm -q gcc44 && export CC=gcc44
             ;;
         *)
             echo "dist undefined, please specify manualy: el5 el6 el7 amzn1 amzn2 amzn2023"
+	    VENDOR=$(rpm --eval '%{?_vendor}')
 	    echo -e "Current OS vendor: $VENDOR \n"
 	    [[ -f /etc/os-release ]] && cat /etc/os-release
 	    [[ -f /etc/redhat-release ]] && cat /etc/redhat-release 
@@ -84,6 +86,7 @@ if [[ -z $rpmtopdir ]]; then
     esac
 fi
 
+[[ $rpmtopdir == "GETEL" ]] && GUESS_DIST && exit 0
 
 if [[ ! -d $rpmtopdir ]]; then 
   echo "only work in el5/el6/el7/amzn1/amzn2/amzn2023"
diff --git a/pullsrc.sh b/pullsrc.sh
index 17340d0..5d487ec 100755
--- a/pullsrc.sh
+++ b/pullsrc.sh
@@ -49,7 +49,7 @@ if [[ ! -f $ASKPASSSRC  ]]; then
 	  echo "!!! Please download $ASKPASSSRC in $PWD by yourself."
 fi
 
-if ! perl -v | grep 'perl 5' && [[ ! -f $PERLSRC  ]]; then
+if [[ $(./compile.sh GETEL) == "el5" ]]; then
   echo Get: $PERLMIR/$PERLSRC
   wget --no-check-certificate $PERLMIR/$PERLSRC || \
 	  echo "!!! Please download $PERLSRC in $PWD by yourself."