diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index a74f69de..3be4849b 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -2,7 +2,10 @@
 
 ## 3.1.8 (2022-03-22)
 
+- feat: add `--profile` flag for har2case to support overwrite headers/cookies with specified yaml/json configuration file
+- feat: support variable and function in response extract expression
 - fix: keep negative index in jmespath unchanged when converting pytest files, e.g. body.users[-1]
+- fix: variable should not start with digit
 - change: load yaml file with FullLoader
 
 ## 3.1.7 (2022-03-22)
diff --git a/httprunner/parser.py b/httprunner/parser.py
index a6e03f2d..457d8806 100644
--- a/httprunner/parser.py
+++ b/httprunner/parser.py
@@ -15,9 +15,10 @@ absolute_http_url_regexp = re.compile(r"^https?://", re.I)
 # use $$ to escape $ notation
 dolloar_regex_compile = re.compile(r"\$\$")
 # variable notation, e.g. ${var} or $var
-variable_regex_compile = re.compile(r"\$\{(\w+)\}|\$(\w+)")
+# variable should start with a-zA-Z_
+variable_regex_compile = re.compile(r"\$\{([a-zA-Z_]\w*)\}|\$([a-zA-Z_]\w*)")
 # function notation, e.g. ${func1($var_1, $var_3)}
-function_regex_compile = re.compile(r"\$\{(\w+)\(([\$\w\.\-/\s=,]*)\)\}")
+function_regex_compile = re.compile(r"\$\{([a-zA-Z_]\w*)\(([\$\w\.\-/\s=,]*)\)\}")
 
 
 def parse_string_value(str_value: Text) -> Any:
diff --git a/tests/parser_test.py b/tests/parser_test.py
index e1eef7fa..2a77af59 100644
--- a/tests/parser_test.py
+++ b/tests/parser_test.py
@@ -41,6 +41,9 @@ class TestParserBasic(unittest.TestCase):
         self.assertEqual(parser.regex_findall_variables("Z:2>1*0*1+1$$$$a"), [])
         self.assertEqual(parser.regex_findall_variables("Z:2>1*0*1+1$$a$b"), ["b"])
         self.assertEqual(parser.regex_findall_variables("Z:2>1*0*1+1$$a$$b"), [])
+        # variable should not start with digit
+        self.assertEqual(parser.regex_findall_variables("$1a"), [])
+        self.assertEqual(parser.regex_findall_variables("${1a}"), [])
 
     def test_extract_variables(self):
         self.assertEqual(parser.extract_variables("$var"), {"var"})
@@ -230,7 +233,8 @@ class TestParserBasic(unittest.TestCase):
         )
 
     def test_parse_data_string_with_functions(self):
-        import random, string
+        import random
+        import string
 
         functions_mapping = {
             "gen_random_string": lambda str_len: "".join(
@@ -243,8 +247,7 @@ class TestParserBasic(unittest.TestCase):
         )
         self.assertEqual(len(result), 5)
 
-        add_two_nums = lambda a, b=1: a + b
-        functions_mapping["add_two_nums"] = add_two_nums
+        functions_mapping["add_two_nums"] = lambda a, b=1: a + b
         self.assertEqual(
             parser.parse_data(
                 "${add_two_nums(1)}", functions_mapping=functions_mapping