Regex operator -> Regular expression (Regex)

What Is a Regular Expression?

A regular expression is like a smart search — it helps the system find patterns in text, not just exact words.

Think of it like telling the system:

"Look for anything that looks like this, not just exactly this."

 

Everyday Analogy:

Supermarket Example

You tell a store assistant:

“I want any fruit that starts with A and ends with E.”

Instead of checking every single word, the assistant understands the pattern and brings you:

• Apple

• Artichoke

That’s what regex does — it looks for matching patterns, not exact words.

 

Easy Examples

1. Find postal codes that start with "23"

Value: ^23

• ^ means “starts with”

• 23 is the number you want

Matches:

• 23456 ✅

• 23999 ✅

• 12345 ❌ (doesn’t start with 23)

 

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2. Find postal codes that end with "89"

Value: 89$

• $ means “ends with”

• 89 is the number you want

Matches:

• 4789 ✅

• 2289 ✅

• 8923 ❌ (doesn’t end with 89)

 

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3. Match any number with exactly 5 digits (like a postal code)

 

Value: ^\d{5}$

• \d means any digit (0–9)

• {5} means exactly 5 digits

• ^ and $ mean “start and end”

Matches:

• 12345 ✅

• 90210 ✅

• 1234 ❌ (only 4 digits)

• 123456 ❌ (too many digits)

 

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4. Match any text that contains the word “Spain”

Value: Spain

Matches:

• Order from Spain ✅

• Shipped to Spain via DHL ✅

• German order ❌

✅ This is the simplest use — just searching for the word.

 

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5. Match emails

Value: [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-z]{2,}

✅ Examples that Match the Pattern

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Postal Code example: ⬇️

1. Postal codes that start with 23

 

Value: ^23

What it means:

• 23000 ✅ (starts with 23) 

• 23456 ✅

• 23999 ✅

Doesn’t match:

• 12345 ❌ (doesn't start with 23)

 

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2. Postal codes that end with 89

 

Value: 89$

What it means:

Matches:

• 4789 ✅ (ends with 89)

• 9989 ✅

Doesn’t match:

• 8912 ❌ (89 is at the start, not the end)

• 12345 ❌

 

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3. Exactly 5-digit postal codes

 

Value: ^\d{5}$

What it means:

So it checks:
➤ “Starts with a digit, has exactly 5 digits, and nothing more after that.”

Matches:

• 12345 ✅(start with a digit, it has only 5 digits, nothing more after that )

• 90210 ✅

Doesn’t match:

• 1234 ❌ (only 4 digits)

• 123456 ❌ (6 digits)

• 12A45 ❌ (contains a letter)

 

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4. Postal codes that contain "00" anywhere

 

Value: 00

What it means:

Matches:

• 10023 ✅

• 23001 ✅

• 80000 ✅

Doesn’t match:

• 12345 ❌

• 23456 ❌

  
  
  

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5. Postal codes that start with 2 and end with 6

 

Value: ^2.*6$

What it means:

.* = Think of it as a “wildcard” — it means "any characters in the middle"

Matches:

• 2006 ✅

• 23456 ✅

• 2v9456✅

• 298456 ✅

Doesn’t match:

• 12346 ❌ (starts with 1, not 2)

• 23457 ❌ (ends with 7, not 6)

 

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6. Postal codes with two values in one field

 

Value: ^(?:(06039|06059))$

This is a regular expression used to match specific postal codes — in this case, either 06039 or 06059.

 

^ ->   The beginning of the string. It means the match must start at the very beginning.

(?:..) -> A non-capturing group. This groups options without saving them for later. Think of it as a simple container.

06039|06059 -> Inside the group, the **pipe (`

$ -> The end of the string. It means the match must end here, with nothing after.

 

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Summary of Common Symbols