diff --git a/regression_test/Makefile.regression b/regression_test/Makefile.regression
index cc34a87f68110c4b4ec653722f0f006711369d1c..7aa8a5076c2a5c073b0e84627dc6676ae0c65860 100644
--- a/regression_test/Makefile.regression
+++ b/regression_test/Makefile.regression
@@ -70,9 +70,9 @@ endif
 ifdef DYN
 DYNAMIC_SUFFIX = -dynamic
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:
 else
-  export LD_LIBRARY_PATH+=:$(TTCN3_DIR)/lib:
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(TTCN3_DIR)/lib:
 endif 
 endif
 
diff --git a/regression_test/XML/XmlWorkflow/bin/prj2mk.pl b/regression_test/XML/XmlWorkflow/bin/prj2mk.pl
index 50e65f19f5bfebc966f3883634f0c68c00057475..063a380f9859975e0910c2d32cbc008d7006532d 100644
--- a/regression_test/XML/XmlWorkflow/bin/prj2mk.pl
+++ b/regression_test/XML/XmlWorkflow/bin/prj2mk.pl
@@ -153,8 +153,8 @@ while (<MAKEFILE_IN>) {
     print MAKEFILE_OUT <<MKF;
 TOPDIR := ../../..
 include   ../../../Makefile.regression
-export PATH+=:\$(TTCN3_DIR)/bin:
-export LD_LIBRARY_PATH+=:\$(ABS_SRC):\$(TTCN3_DIR)/lib:
+export PATH:=\$(PATH):\$(TTCN3_DIR)/bin:
+export LD_LIBRARY_PATH:=\$(LD_LIBRARY_PATH):\$(ABS_SRC):\$(TTCN3_DIR)/lib:
 MKF
   }
 }
diff --git a/regression_test/XML/XmlWorkflow/bin2/prj2mk.pl b/regression_test/XML/XmlWorkflow/bin2/prj2mk.pl
index 0530b685570a03ec4d69a8ff314104642e4e55f9..903a8f049923dbef772d549747d52931681f25b7 100644
--- a/regression_test/XML/XmlWorkflow/bin2/prj2mk.pl
+++ b/regression_test/XML/XmlWorkflow/bin2/prj2mk.pl
@@ -131,8 +131,8 @@ while (<MAKEFILE_IN>) {
     print MAKEFILE_OUT <<MKF;
 TOPDIR := ../../..
 include   ../../../Makefile.regression
-export PATH+=:\$(TTCN3_DIR)/bin:
-export LD_LIBRARY_PATH+=:\$(ABS_SRC):\$(TTCN3_DIR)/lib:
+export PATH:=\$(PATH):\$(TTCN3_DIR)/bin:
+export LD_LIBRARY_PATH:=\$(LD_LIBRARY_PATH):\$(ABS_SRC):\$(TTCN3_DIR)/lib:
 MKF
   }
 }
diff --git a/regression_test/cfgFile/define/macro_reference/Makefile b/regression_test/cfgFile/define/macro_reference/Makefile
index 282a6201832332d73a9a0cdf504ee236b9856aee..f04974d30286c422876a93027a7b2a5817608159 100644
--- a/regression_test/cfgFile/define/macro_reference/Makefile
+++ b/regression_test/cfgFile/define/macro_reference/Makefile
@@ -35,9 +35,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/define/structured/Makefile b/regression_test/cfgFile/define/structured/Makefile
index d7defc99245e04a4601c9ed08104b43ae14a5679..db402b2c38677b482e742902f72480964a3b56ff 100644
--- a/regression_test/cfgFile/define/structured/Makefile
+++ b/regression_test/cfgFile/define/structured/Makefile
@@ -35,9 +35,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/module_parameters/assignment/Makefile b/regression_test/cfgFile/module_parameters/assignment/Makefile
index 5d63334a97236a9bdd6e62ed6bf658e567eb33c0..58f50b46553207d1ccd045320b037119ad63f9b1 100644
--- a/regression_test/cfgFile/module_parameters/assignment/Makefile
+++ b/regression_test/cfgFile/module_parameters/assignment/Makefile
@@ -30,9 +30,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/module_parameters/concat/Makefile b/regression_test/cfgFile/module_parameters/concat/Makefile
index 1121a0e8b592916dd242b980a7c90785c07ab837..7fadfb27ad29364e30b2cc9ae3bcb1b142db0a16 100644
--- a/regression_test/cfgFile/module_parameters/concat/Makefile
+++ b/regression_test/cfgFile/module_parameters/concat/Makefile
@@ -30,9 +30,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/module_parameters/nested/Makefile b/regression_test/cfgFile/module_parameters/nested/Makefile
index 37ab050d2ef4859c13719547e704c09fa0aaec6d..179169b78ff30f1b4ad76eab03ae3559d369ce6d 100644
--- a/regression_test/cfgFile/module_parameters/nested/Makefile
+++ b/regression_test/cfgFile/module_parameters/nested/Makefile
@@ -26,9 +26,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/module_parameters/references/Makefile b/regression_test/cfgFile/module_parameters/references/Makefile
index 9af8204084af62ac3c7ffa6e98bc52a827a3260e..8260aaa6fd0303c5362a1aa5f0bdcbd7bcf15088 100644
--- a/regression_test/cfgFile/module_parameters/references/Makefile
+++ b/regression_test/cfgFile/module_parameters/references/Makefile
@@ -28,9 +28,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/module_parameters/special_values/Makefile b/regression_test/cfgFile/module_parameters/special_values/Makefile
index 41129fef64a3864c36b6104b1434f0f39370471d..b899408dd4f0ab9f5bde904e406b6b9e5fe3daaa 100644
--- a/regression_test/cfgFile/module_parameters/special_values/Makefile
+++ b/regression_test/cfgFile/module_parameters/special_values/Makefile
@@ -26,9 +26,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/ordered_include/Makefile b/regression_test/cfgFile/ordered_include/Makefile
index 54dc21725b054906a25d513860511680d09f3688..eba9be9bcea4b3b9944cf0272ff6d995e5d8117d 100644
--- a/regression_test/cfgFile/ordered_include/Makefile
+++ b/regression_test/cfgFile/ordered_include/Makefile
@@ -31,9 +31,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/cfgFile/testport_parameters/Makefile b/regression_test/cfgFile/testport_parameters/Makefile
index 906e8069786fa5dea1f94c2b7d9659931a6997ac..bc8efad89319388e66239e6de9c4c1da757ebc77 100644
--- a/regression_test/cfgFile/testport_parameters/Makefile
+++ b/regression_test/cfgFile/testport_parameters/Makefile
@@ -31,9 +31,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif 
 endif
 
diff --git a/regression_test/fuzzy/Makefile b/regression_test/fuzzy/Makefile
index 28987ae339418ad1d99dc13efac9029b14ffecd6..d432da0176a5090b9da59409e77f58ba8164a425 100644
--- a/regression_test/fuzzy/Makefile
+++ b/regression_test/fuzzy/Makefile
@@ -28,9 +28,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif
 DYNFLAG := -l
 endif
diff --git a/regression_test/templateExclusiveRange/Makefile b/regression_test/templateExclusiveRange/Makefile
index 231061bb6b600bf230c2041e98a79b38e6def4ff..12c7654a327c98fb7bd05d9f32a616c644ca915f 100644
--- a/regression_test/templateExclusiveRange/Makefile
+++ b/regression_test/templateExclusiveRange/Makefile
@@ -26,9 +26,9 @@ endif
 
 ifdef DYN
 ifeq ($(PLATFORM), WIN32)
-  export PATH+=:$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export PATH:=$(PATH):$(TTCN3_DIR)/lib:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 else
-  export LD_LIBRARY_PATH+=:$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
+  export LD_LIBRARY_PATH:=$(LD_LIBRARY_PATH):$(ABS_SRC)/$(DIR_SINGLE):$(ABS_SRC)/$(DIR_PARALLEL):
 endif
 DYNFLAG := -l
 endif