diff --git a/entrypoint.sh b/entrypoint.sh
index 49f2881..8532dd9 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -17,22 +17,22 @@ main() {
     echo "could not read previous version"; exit 1
   fi
 
-  possible_release_types="major feature minor bug patch hotfix alpha beta pre rc"
+  possible_release_types=(major feature minor bug patch hotfix alpha beta pre rc)
 
-  if [[ ! ${possible_release_types[*]} =~ ${release_type} ]]; then
+  if [[ ! " ${possible_release_types[*]} " =~ " ${release_type} " ]]; then
     echo "valid argument: [ ${possible_release_types[*]} ]"; exit 1
   fi
 
   major=0; minor=0; patch=0; pre=""; preversion=0
 
-  # break down the version number into it's components
-  regex="^v?([0-9]+)\.([0-9]+)\.([0-9]+)(-([a-z]+)(\.[0-9]+)?)?$"
+  # break down the version number into its components
+  regex="^v?([0-9]+)\.([0-9]+)\.([0-9]+)(-([a-z]+)(\\.([0-9]+))?)?$"
   if [[ $prev_version =~ $regex ]]; then
     major="${BASH_REMATCH[1]}"
     minor="${BASH_REMATCH[2]}"
     patch="${BASH_REMATCH[3]}"
     pre="${BASH_REMATCH[5]}"
-    preversion="${BASH_REMATCH[6]}"
+    preversion="${BASH_REMATCH[7]}"
   else
     echo "previous version '$prev_version' is not a semantic version"
     exit 1
@@ -46,54 +46,13 @@ main() {
     ((++minor)); patch=0; pre="";;
   "bug"|"patch"|"hotfix")
     ((++patch)); pre="";;
-  "alpha")
-    if [[ -z "$preversion" ]];
-      then
-        preversion=0
-      else
-        if [[ "$pre" != "-alpha" ]];
-          then
-          preversion=1
-          else ((++preversion))
-        fi
+  "alpha"|"beta"|"pre"|"rc")
+    if [[ "$pre" != "$release_type" ]]; then
+      preversion=1
+    else
+      ((++preversion))
     fi
-    pre="-alpha.$preversion";;
-  "beta")
-    if [[ -z "$preversion" ]];
-      then
-        preversion=0
-      else
-        if [[ "$pre" != "-beta" ]];
-          then
-          preversion=1
-          else ((++preversion))
-        fi
-    fi
-    pre="-beta.$preversion";;
-  "pre")
-    if [[ -z "$preversion" ]];
-      then
-        preversion=0
-      else
-        if [[ "$pre" != "-pre" ]];
-          then
-          preversion=1
-          else ((++preversion))
-        fi
-    fi
-    pre="-pre.$preversion";;
-  "rc")
-    if [[ -z "$preversion" ]];
-      then
-        preversion=0
-      else
-        if [[ "$pre" != "-rc" ]];
-          then
-          preversion=1
-          else ((++preversion))
-        fi
-    fi
-    pre="-rc.$preversion";;
+    pre="-$release_type.$preversion";;
   esac
 
   next_version="${major}.${minor}.${patch}${pre}"