diff --git a/coconut/compiler/compiler.py b/coconut/compiler/compiler.py
index 036aefc25..21be94792 100644
--- a/coconut/compiler/compiler.py
+++ b/coconut/compiler/compiler.py
@@ -1630,16 +1630,8 @@ def str_proc(self, inputstring, **kwargs):
 
                 # start the string hold if we're at the start of a string
                 if hold is not None:
-                    is_f = False
-                    j = i - len(hold["start"])
-                    while j >= 0:
-                        prev_c = inputstring[j]
-                        if prev_c == "f":
-                            is_f = True
-                            break
-                        elif prev_c != "r":
-                            break
-                        j -= 1
+                    is_f_check_str = inputstring[clip(i - len(hold["start"]) + 1 - self.start_f_str_regex_len, min=0): i - len(hold["start"]) + 1]
+                    is_f = self.start_f_str_regex.search(is_f_check_str)
                     if is_f:
                         hold.update({
                             "type": "f string",
diff --git a/coconut/compiler/grammar.py b/coconut/compiler/grammar.py
index 0a30dd146..3cf73fb22 100644
--- a/coconut/compiler/grammar.py
+++ b/coconut/compiler/grammar.py
@@ -817,7 +817,7 @@ class Grammar(object):
         octint = combine(Word("01234567") + ZeroOrMore(underscore.suppress() + Word("01234567")))
         hexint = combine(Word(hexnums) + ZeroOrMore(underscore.suppress() + Word(hexnums)))
 
-        imag_j = caseless_literal("j") | fixto(caseless_literal("i", suppress=True), "j")
+        imag_j = caseless_literal("j") | fixto(caseless_literal("i", suppress=True, disambiguate=True), "j")
         basenum = combine(
             Optional(integer) + dot + integer
             | integer + Optional(dot + Optional(integer))
@@ -2660,6 +2660,9 @@ class Grammar(object):
             | fixto(end_of_line, "misplaced newline (maybe missing ':')")
         )
 
+        start_f_str_regex = compile_regex(r"\br?fr?$")
+        start_f_str_regex_len = 4
+
         end_f_str_expr = combine(start_marker + (rbrace | colon | bang))
 
         string_start = start_marker + python_quoted_string
diff --git a/coconut/compiler/util.py b/coconut/compiler/util.py
index 4d7074ca6..5e2cd75ac 100644
--- a/coconut/compiler/util.py
+++ b/coconut/compiler/util.py
@@ -131,6 +131,7 @@
     cache_validation_info,
     require_cache_clear_frac,
     reverse_any_of,
+    all_keywords,
 )
 from coconut.exceptions import (
     CoconutException,
@@ -1537,12 +1538,16 @@ def any_len_perm_at_least_one(*elems, **kwargs):
     return any_len_perm_with_one_of_each_group(*groups_and_elems)
 
 
-def caseless_literal(literalstr, suppress=False):
+def caseless_literal(literalstr, suppress=False, disambiguate=False):
     """Version of CaselessLiteral that always parses to the given literalstr."""
+    out = CaselessLiteral(literalstr)
     if suppress:
-        return CaselessLiteral(literalstr).suppress()
+        out = out.suppress()
     else:
-        return fixto(CaselessLiteral(literalstr), literalstr)
+        out = fixto(out, literalstr)
+    if disambiguate:
+        out = disallow_keywords(k for k in all_keywords if k.startswith((literalstr[0].lower(), literalstr[0].upper()))) + out
+    return out
 
 
 # -----------------------------------------------------------------------------------------------------------------------
diff --git a/coconut/constants.py b/coconut/constants.py
index 86f1592bc..146c9210e 100644
--- a/coconut/constants.py
+++ b/coconut/constants.py
@@ -37,7 +37,7 @@ def fixpath(path):
     return os.path.normpath(os.path.realpath(os.path.expanduser(path)))
 
 
-def get_bool_env_var(env_var, default=False):
+def get_bool_env_var(env_var, default=None):
     """Get a boolean from an environment variable."""
     boolstr = os.getenv(env_var, "").lower()
     if boolstr in ("true", "yes", "on", "1", "t"):
diff --git a/coconut/root.py b/coconut/root.py
index ffe859e89..22fca3377 100644
--- a/coconut/root.py
+++ b/coconut/root.py
@@ -26,7 +26,7 @@
 VERSION = "3.0.4"
 VERSION_NAME = None
 # False for release, int >= 1 for develop
-DEVELOP = 12
+DEVELOP = 13
 ALPHA = False  # for pre releases rather than post releases
 
 assert DEVELOP is False or DEVELOP >= 1, "DEVELOP must be False or an int >= 1"
diff --git a/coconut/terminal.py b/coconut/terminal.py
index 7247c7641..ee1a9335c 100644
--- a/coconut/terminal.py
+++ b/coconut/terminal.py
@@ -210,7 +210,7 @@ def __init__(self, other=None):
     @classmethod
     def enable_colors(cls, file=None):
         """Attempt to enable CLI colors."""
-        use_color = get_bool_env_var(use_color_env_var)
+        use_color = get_bool_env_var(use_color_env_var, default=None)
         if (
             use_color is False
             or use_color is None and file is not None and not isatty(file)
diff --git a/coconut/tests/src/cocotest/agnostic/primary_2.coco b/coconut/tests/src/cocotest/agnostic/primary_2.coco
index ccee37e55..3d7acdbd8 100644
--- a/coconut/tests/src/cocotest/agnostic/primary_2.coco
+++ b/coconut/tests/src/cocotest/agnostic/primary_2.coco
@@ -424,6 +424,10 @@ def primary_test_2() -> bool:
     assert all_equal([], to=10)
     assert all_equal([10; 10; 10; 10], to=10)
     assert not all_equal([1, 1], to=10)
+    assert not 0in[1,2,3]
+    if"0":assert True
+    if"0":
+        assert True
 
     with process_map.multiple_sequential_calls():  # type: ignore
         assert map((+), range(3), range(4)$[:-1], strict=True) |> list == [0, 2, 4] == process_map((+), range(3), range(4)$[:-1], strict=True) |> list  # type: ignore