diff --git a/grammar/culebra.peg b/grammar/culebra.peg
new file mode 100644
index 0000000..d3e0990
--- /dev/null
+++ b/grammar/culebra.peg
@@ -0,0 +1,51 @@
+
+    PROGRAM               <-  _ STATEMENTS
+
+    STATEMENTS            <-  (EXPRESSION (';' _)?)*
+
+    EXPRESSION            <-  ASSIGNMENT / PRIMARY
+    ASSIGNMENT            <-  MUTABLE IDENTIFIER '=' _ EXPRESSION
+    WHILE                 <-  'while' _ EXPRESSION BLOCK
+    IF                    <-  'if' _ EXPRESSION BLOCK ('else' _ 'if' _ EXPRESSION BLOCK)* ('else' _ BLOCK)?
+    FUNCTION              <-  'fn' _ PARAMETERS BLOCK
+    PARAMETERS            <-  '(' _ (PARAMETER (',' _ PARAMETER)*)? ')' _
+    PARAMETER             <-  MUTABLE IDENTIFIER
+    FUNCTION_CALL         <-  IDENTIFIER ARGUMENTS
+    ARGUMENTS             <-  '(' _ (EXPRESSION (', ' _ EXPRESSION)*)? ')' _
+
+    PRIMARY               <-  LOGICAL_OR ('||' _ LOGICAL_OR)*
+    LOGICAL_OR            <-  LOGICAL_AND ('&&' _  LOGICAL_AND)*
+    LOGICAL_AND           <-  CONDITION (CONDITION_OPERATOR CONDITION)*
+    CONDITION             <-  TERM (TERM_OPERATOR TERM)*
+    TERM                  <-  UNARY_PLUS_OPERATOR? UNARY_PLUS
+    UNARY_PLUS            <-  UNARY_MINUS_OPERATOR? UNARY_MINUS
+    UNARY_MINUS           <-  UNARY_NOT_OPERATOR? UNARY_NOT
+    UNARY_NOT             <-  FACTOR (FACTOR_OPERATOR FACTOR)*
+    FACTOR                <-  WHILE / IF / FUNCTION / FUNCTION_CALL / NUMBER / BOOLEAN / STRING / INTERPOLATED_STRING / IDENTIFIER / '(' _ EXPRESSION ')' _
+
+    BLOCK                 <-  '{' _ STATEMENTS '}' _
+
+    CONDITION_OPERATOR    <-  < ('==' / '!=' / '<=' / '<' / '>=' / '>') > _
+    TERM_OPERATOR         <-  < [-+] > _
+    UNARY_PLUS_OPERATOR   <-  < '+' > _
+    UNARY_MINUS_OPERATOR  <-  < '-' > _
+    UNARY_NOT_OPERATOR    <-  < '!' > _
+    FACTOR_OPERATOR       <-  < [*/%] > _
+
+    IDENTIFIER            <-  < [a-zA-Z_][a-zA-Z0-9_]* > _
+
+    NUMBER                <-  < [0-9]+ > _
+    BOOLEAN               <-  < ('true' / 'false') > _
+    STRING                <-  ['] < (!['] .)* > ['] _
+
+    INTERPOLATED_STRING   <-  '"' ('{' _ EXPRESSION '}' / INTERPOLATED_CONTENT)* '"' _
+    INTERPOLATED_CONTENT  <-  (!["{] .) (!["{] .)*
+
+    MUTABLE               <-  < 'mut'? > _
+
+    ~_                    <-  (Space / EndOfLine / Comment)*
+    Space                 <-  ' ' / '\t'
+    EndOfLine             <-  '\r\n' / '\n' / '\r'
+    EndOfFile             <-  !.
+    Comment               <-  '/*' (!'*/' .)* '*/' /  ('#' / '//') (!(EndOfLine / EndOfFile) .)* (EndOfLine / EndOfFile)
+