diff --git a/benches/file.rs b/benches/file.rs
index ab9e21b..b35831e 100644
--- a/benches/file.rs
+++ b/benches/file.rs
@@ -52,32 +52,32 @@ fn bench_split_lines(data: &str, b: &mut test::Bencher) {
 }
 
 #[bench]
-fn parse_words_lines_empty(b: &mut test::Bencher) {
+fn parse_lines_empty(b: &mut test::Bencher) {
     bench_split_lines(data::EMPTY, b);
 }
 
 #[bench]
-fn parse_words_lines_no_tokens(b: &mut test::Bencher) {
+fn parse_lines_no_tokens(b: &mut test::Bencher) {
     bench_split_lines(data::NO_TOKENS, b);
 }
 
 #[bench]
-fn parse_words_lines_single_token(b: &mut test::Bencher) {
+fn parse_lines_single_token(b: &mut test::Bencher) {
     bench_split_lines(data::SINGLE_TOKEN, b);
 }
 
 #[bench]
-fn parse_words_lines_sherlock(b: &mut test::Bencher) {
+fn parse_lines_sherlock(b: &mut test::Bencher) {
     bench_split_lines(data::SHERLOCK, b);
 }
 
 #[bench]
-fn parse_words_lines_code(b: &mut test::Bencher) {
+fn parse_lines_code(b: &mut test::Bencher) {
     bench_split_lines(data::CODE, b);
 }
 
 #[bench]
-fn parse_words_lines_corpus(b: &mut test::Bencher) {
+fn parse_lines_corpus(b: &mut test::Bencher) {
     bench_split_lines(data::CORPUS, b);
 }
 
diff --git a/src/config.rs b/src/config.rs
index 2c73aba..9880df0 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -53,22 +53,32 @@ pub trait FileSource {
         None
     }
 
-    /// Verifying spelling in filess.
+    /// Verifying spelling in files.
     fn check_file(&self) -> Option<bool> {
         None
     }
 
-    /// Do not check identifiers that appear to be hexadecimal values
+    /// Do not check identifiers that appear to be hexadecimal values.
     fn ignore_hex(&self) -> Option<bool> {
         None
     }
 
-    /// Allow identifiers to include digits, in addition to letters
+    /// Allow identifiers to start with digits, in addition to letters.
+    fn identifier_leading_digits(&self) -> Option<bool> {
+        None
+    }
+
+    /// Allow identifiers to start with one of these characters.
+    fn identifier_leading_chars(&self) -> Option<&str> {
+        None
+    }
+
+    /// Allow identifiers to include digits, in addition to letters.
     fn identifier_include_digits(&self) -> Option<bool> {
         None
     }
 
-    /// Specify additional characters to be included in identifiers
+    /// Allow identifiers to include these characters.
     fn identifier_include_chars(&self) -> Option<&str> {
         None
     }
@@ -233,6 +243,8 @@ pub struct FileConfig {
     pub check_filename: Option<bool>,
     pub check_file: Option<bool>,
     pub ignore_hex: Option<bool>,
+    pub identifier_leading_digits: Option<bool>,
+    pub identifier_leading_chars: Option<String>,
     pub identifier_include_digits: Option<bool>,
     pub identifier_include_chars: Option<String>,
 }
@@ -248,6 +260,12 @@ impl FileConfig {
         if let Some(source) = source.ignore_hex() {
             self.ignore_hex = Some(source);
         }
+        if let Some(source) = source.identifier_leading_digits() {
+            self.identifier_leading_digits = Some(source);
+        }
+        if let Some(source) = source.identifier_leading_chars() {
+            self.identifier_leading_chars = Some(source.to_owned());
+        }
         if let Some(source) = source.identifier_include_digits() {
             self.identifier_include_digits = Some(source);
         }
@@ -268,6 +286,17 @@ impl FileConfig {
         self.ignore_hex.unwrap_or(true)
     }
 
+    pub fn identifier_leading_digits(&self) -> bool {
+        self.identifier_leading_digits.unwrap_or(false)
+    }
+
+    pub fn identifier_leading_chars(&self) -> &str {
+        self.identifier_leading_chars
+            .as_ref()
+            .map(|s| s.as_str())
+            .unwrap_or("_")
+    }
+
     pub fn identifier_include_digits(&self) -> bool {
         self.identifier_include_digits.unwrap_or(true)
     }
@@ -293,6 +322,14 @@ impl FileSource for FileConfig {
         self.ignore_hex
     }
 
+    fn identifier_leading_digits(&self) -> Option<bool> {
+        self.identifier_leading_digits
+    }
+
+    fn identifier_leading_chars(&self) -> Option<&str> {
+        self.identifier_leading_chars.as_ref().map(|s| s.as_str())
+    }
+
     fn identifier_include_digits(&self) -> Option<bool> {
         self.identifier_include_digits
     }
diff --git a/src/main.rs b/src/main.rs
index 86fdf9a..d942aa4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -412,6 +412,8 @@ fn run() -> Result<i32, anyhow::Error> {
 
         let parser = typos::tokens::ParserBuilder::new()
             .ignore_hex(config.default.ignore_hex())
+            .leading_digits(config.default.identifier_leading_digits())
+            .leading_chars(config.default.identifier_leading_chars().to_owned())
             .include_digits(config.default.identifier_include_digits())
             .include_chars(config.default.identifier_include_chars().to_owned())
             .build();
diff --git a/typos/src/tokens.rs b/typos/src/tokens.rs
index 883f1a5..91b6784 100644
--- a/typos/src/tokens.rs
+++ b/typos/src/tokens.rs
@@ -9,6 +9,8 @@ pub enum Case {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct ParserBuilder {
     ignore_hex: bool,
+    leading_digits: bool,
+    leading_chars: String,
     include_digits: bool,
     include_chars: String,
 }
@@ -23,6 +25,16 @@ impl ParserBuilder {
         self
     }
 
+    pub fn leading_digits(&mut self, yes: bool) -> &mut Self {
+        self.leading_digits = yes;
+        self
+    }
+
+    pub fn leading_chars(&mut self, chars: String) -> &mut Self {
+        self.leading_chars = chars;
+        self
+    }
+
     pub fn include_digits(&mut self, yes: bool) -> &mut Self {
         self.include_digits = yes;
         self
@@ -34,31 +46,44 @@ impl ParserBuilder {
     }
 
     pub fn build(&self) -> Parser {
-        let mut pattern = r#"\b(\p{Alphabetic}"#.to_owned();
-        if self.include_digits {
-            pattern.push_str(r#"|\d"#);
-        }
-        for grapheme in
-            unicode_segmentation::UnicodeSegmentation::graphemes(self.include_chars.as_str(), true)
-        {
-            let escaped = regex::escape(&grapheme);
-            pattern.push_str(&format!("|{}", escaped));
-        }
-        pattern.push_str(r#")+\b"#);
+        let mut pattern = r#"\b("#.to_owned();
+        Self::push_pattern(&mut pattern, self.leading_digits, &self.leading_chars);
+        Self::push_pattern(&mut pattern, self.include_digits, &self.include_chars);
+        pattern.push_str(r#"*)\b"#);
+        let pattern = dbg!(pattern);
+
         let words_str = regex::Regex::new(&pattern).unwrap();
         let words_bytes = regex::bytes::Regex::new(&pattern).unwrap();
+
         Parser {
             words_str,
             words_bytes,
-            ignore_hex: self.ignore_hex && self.include_digits,
+            // `leading_digits` let's us bypass the regexes since you can't have a decimal or
+            // hexadecimal number without a leading digit.
+            ignore_numbers: self.leading_digits,
+            ignore_hex: self.ignore_hex && self.leading_digits,
         }
     }
+
+    fn push_pattern(pattern: &mut String, digits: bool, chars: &str) {
+        pattern.push_str(r#"(\p{Alphabetic}"#);
+        if digits {
+            pattern.push_str(r#"|\d"#);
+        }
+        for grapheme in unicode_segmentation::UnicodeSegmentation::graphemes(chars, true) {
+            let escaped = regex::escape(&grapheme);
+            pattern.push_str(&format!("|{}", escaped));
+        }
+        pattern.push_str(r#")"#);
+    }
 }
 
 impl Default for ParserBuilder {
     fn default() -> Self {
         Self {
             ignore_hex: true,
+            leading_digits: false,
+            leading_chars: "_".to_owned(),
             include_digits: true,
             include_chars: "_'".to_owned(),
         }
@@ -69,6 +94,7 @@ impl Default for ParserBuilder {
 pub struct Parser {
     words_str: regex::Regex,
     words_bytes: regex::bytes::Regex,
+    ignore_numbers: bool,
     ignore_hex: bool,
 }
 
@@ -95,12 +121,12 @@ impl Parser {
     }
 
     fn accept(&self, contents: &[u8]) -> bool {
-        if is_number(contents) {
+        if self.ignore_numbers && is_number(contents) {
             return false;
-        };
+        }
 
-        if self.ignore_hex {
-            return !is_hex(contents);
+        if self.ignore_hex && is_hex(contents) {
+            return false;
         }
 
         true
@@ -455,7 +481,10 @@ mod test {
 
     #[test]
     fn tokenize_ignore_hex_disabled() {
-        let parser = ParserBuilder::new().ignore_hex(false).build();
+        let parser = ParserBuilder::new()
+            .ignore_hex(false)
+            .leading_digits(true)
+            .build();
 
         let input = "Hello 0xDEADBEEF World";
         let expected: Vec<Identifier> = vec![