diff --git a/examples/python2.g b/examples/python2.g
index e8ebda8..a429512 100644
--- a/examples/python2.g
+++ b/examples/python2.g
@@ -145,11 +145,11 @@ number: DEC_NUMBER | HEX_NUMBER | OCT_NUMBER | FLOAT | IMAG_NUMBER
 string: STRING | LONG_STRING
 // Tokens
 
-COMMENT: /\#[^\n]*/
+COMMENT: /#[^\n]*/
 _NEWLINE: ( /\r?\n[\t ]*/ | COMMENT )+
 
 %ignore /[\t \f]+/  // WS
-%ignore /\\\\[\t \f]*\r?\n/   // LINE_CONT 
+%ignore /\\[\t \f]*\r?\n/   // LINE_CONT
 %ignore COMMENT
 
 
diff --git a/examples/python3.g b/examples/python3.g
index bb5a4e8..c27b7ec 100644
--- a/examples/python3.g
+++ b/examples/python3.g
@@ -170,7 +170,7 @@ _NEWLINE: ( /\r?\n[\t ]*/ | COMMENT )+
 
 
 %ignore /[\t \f]+/  // WS
-%ignore /\\\\[\t \f]*\r?\n/   // LINE_CONT 
+%ignore /\\[\t \f]*\r?\n/   // LINE_CONT
 %ignore COMMENT
 
 
diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index f04e3c0..6f2e102 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -18,6 +18,8 @@ from .tree import Tree as T, Transformer, InlineTransformer, Visitor
 __path__ = os.path.dirname(__file__)
 IMPORT_PATHS = [os.path.join(__path__, 'grammars')]
 
+_RE_FLAGS = 'imslux'
+
 _TOKEN_NAMES = {
     '.' : 'DOT',
     ',' : 'COMMA',
@@ -70,7 +72,7 @@ TOKENS = {
     'RULE': '!?[_?]?[a-z][_a-z0-9]*',
     'TOKEN': '_?[A-Z][_A-Z0-9]*',
     'STRING': r'"(\\"|\\\\|[^"\n])*?"i?',
-    'REGEXP': r'/(?!/)(\\/|\\\\|[^/\n])*?/i?',
+    'REGEXP': r'/(?!/)(\\/|\\\\|[^/\n])*?/[%s]?' % _RE_FLAGS,
     '_NL': r'(\r?\n)+\s*',
     'WS': r'[ \t]+',
     'COMMENT': r'//[^\n]*',
@@ -287,7 +289,7 @@ class ExtractAnonTokens(InlineTransformer):
 
 def _literal_to_pattern(literal):
     v = literal.value
-    if v[-1] in 'i':
+    if v[-1] in _RE_FLAGS:
         flags = v[-1]
         v = v[:-1]
     else:
@@ -295,7 +297,7 @@ def _literal_to_pattern(literal):
 
     assert v[0] == v[-1] and v[0] in '"/'
     x = v[1:-1]
-    x = re.sub(r'(\\[wd/]|\\\[|\\\])', r'\\\1', x)
+    x = re.sub(r'(\\[wd/ ]|\\\[|\\\])', r'\\\1', x)
     x = x.replace("'", r"\'")
     s = literal_eval("u'''%s'''" % x)
     return { 'STRING': PatternStr,
diff --git a/lark/tools/nearley.py b/lark/tools/nearley.py
index 107b8ae..5e277a1 100644
--- a/lark/tools/nearley.py
+++ b/lark/tools/nearley.py
@@ -26,7 +26,7 @@ nearley_grammar = r"""
     rule: NAME
     string: STRING
     regexp: REGEXP
-    JS: /(?s){%.*?%}/
+    JS: /{%.*?%}/s
     js: JS?
 
     NAME: /[a-zA-Z_$]\w*/