We use the javascript implementation of RegExp to evaluate regular expressions. Most letters stand for themselves when matching but there are exceptions. Here is a list we have adapted from "Learn RegEx". site
<table border="1" cellpadding="8" cellspacing="0" style="border-collapse:collapse;"> <thead> <tr> <th align="center">Meta character</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td align="center">.</td> <td>Period matches any single character except a line break.</td> </tr> <tr> <td align="center">[ ]</td> <td>Character class. Matches any character contained between the square brackets.</td> </tr> <tr> <td align="center"></td> <td>Negated character class. Matches any character that is not contained between the square brackets</td> </tr> <tr> <td align="center">*</td> <td>Matches 0 or more repetitions of the preceding symbol.</td> </tr> <tr> <td align="center">+</td> <td>Matches 1 or more repetitions of the preceding symbol.</td> </tr> <tr> <td align="center">?</td> <td>Makes the preceding symbol optional.</td> </tr> <tr> <td align="center">{n,m}</td> <td>Braces. Matches at least "n" but not more than "m" repetitions of the preceding symbol.</td> </tr> <tr> <td align="center">(xyz)</td> <td>Character group. Matches the characters xyz in that exact order.</td> </tr> <tr> <td align="center">|</td> <td>Alternation. Matches either the characters before or the characters after the symbol.</td> </tr> <tr> <td align="center">\</td> <td>Escapes the next character. This allows you to match reserved characters <code>[ ] ( ) { } . * + ? ^ $ \ |</code></td> </tr> <tr> <td align="center">^</td> <td>Matches the beginning of the input.</td> </tr> <tr> <td align="center">{body}lt;/td> <td>Matches the end of the input.</td> </tr> </tbody>