寻求可匹配三类特定模式的Perl正则表达式

算力阿峰

2026-5-21

Hey there! Let me lay out these Markdown formatting rules in a clean, easy-to-follow way with practical examples:

Markdown Formatting Rules Cheat Sheet

Below are the core formatting conventions you asked about, each with a clear demo:

Headings: Use number signs (#) to define heading levels. More #s mean smaller headings (1-6 levels total).
- Example: ## Secondary Heading renders as:
  Secondary Heading
List Items: Start each list entry with a dash (-). Indent nested items with spaces or tabs to create hierarchy.
- Example:
```
- First main item
- Second main item
  - Nested sub-item
```
  Renders as:
  - First main item
  - Second main item
    - Nested sub-item
Emphasized Text: Wrap text with asterisks (*) for italics, or double asterisks for bold.
- Italic: *This is italicized* → This is italicized
- Bold: **This is bolded** → This is bolded
Code/Commands: Use single backticks (`) for inline code, or triple backticks (```) for multi-line code blocks.
- Inline code: print("Hello World")
- Multi-line code block example:
```
# Sample Perl code
my $message = "Hello from Perl!";
print $message;
```
Quoted Text: Prepend lines with a greater-than sign (>) to create blockquotes. Nest quotes by adding more >s.
- Example:
```
> Original quote
> > Nested quote
```
  Renders as:
  Original quote
  Nested quote
Links: Format as [Link Text](URL). The text in brackets is what's displayed, the URL in parentheses is the target.
- Example: [Markdown Guide](https://www.markdownguide.org) → Markdown Guide
Images: Similar to links, but start with an exclamation mark: ![Alt Text](Image URL). Alt text describes the image for accessibility.
- Example: ![Sample Image](https://example.com/image.jpg)