Using Conditional Expressions

Conditional expressions help qualify and restrict regex searches, increasing the probability of a desirable match. The vertical bar "|" symbol, meaning "OR", places a condition on the regex to search for either one character in a string or another. Because the regex has a list of alternate choices to evaluate, this regex technique is called "alternation". To search for either one character or another, insert a vertical bar "|" between the desired characters.

Example 1: Use "|" to alternate a search for various spellings of a string.

Regex:
```
gray|grey
```
Matches:
```
gray
grey
```
Doesn't Match:
```
GREY
Gray
```

Example 2: Use "|" to alternate a search for either email or Email or EMAIL or e-mail.

Regex:
```
email|Email|EMAIL|e-mail
```
Matches:
```
email
Email
EMAIL
e-mail
```
Doesn't Match:
```
EmAiL
E-Mail
```