Validate a line in quotes. Return one (and only one) backreference with the text. ie: quoted text from "quoted text". Note: a \ escapes any char, so \" is a valid escape.

Use substitution to put commas in all numbers to separate the thousands. ie: 12345678 → 12,345,678. The number could be in a sentence, and there may be more than one number in the sentence.

Replace every other character if it's a \d with * (only those in even positions: 2, 4, 6, etc). Example: a1b2cde3g45hi6 should become abcdeg4hi6

VALIDATING IP V4 1.1.1.1 2.2.2.2 3.3.3.3 4.4.4.4 5.5.5.5...

This is a test

Verify that a given e-mail address is valid. We all know how complex emails are, but despite this, let's give it a try and see what we can come up with. You could start by trying to match contact@regex101.com (denoted as @.).

For every occurrence of the char #, match the previous character and save it in a group (backreference). Example: for the text "a#bc# -#", set backreferences with a, c and -. You are not allowed to consume the hash character.

Check if a floating point number (e.g. 3.14159) is in a valid format.

Strip all HTML tags from a string. HTML tags are enclosed in . The regex will be applied on a line-by-line basis, meaning partial tags will need to be handled by the regex. Don't worry about opening or closing tags; we just want to get rid of them all. Note: This task is meant to be a learning exe...

Could you help me validate my input and only match positive integers between the range of 0 and 100? There can be several numbers in a string which I would want to retrieve. Try out these example strings: ...

Validate an IPv4 address. The addresses are four numbered separated by three dots, and can only have a maximum value of 255 in either octet. Start by trying to validate 172.16.254.1.

I'm trying to match bit sequences which are alternating between 1 and 0 and never have more than one 1 or 0 in a row. They can be single digits. Try matching this: 0101010, 1010101010 or 1

Oh no! It seems my friends spilled beer all over my keyboard last night and my keys are super sticky now. Some of the time whennn I press a key, I get two duplicates. Can you ppplease help me fix thhhis? Substitute with $1

Match a string that contains any of the following substrings: http://, www., porn, or credit card. But don't match the text if it contains one of: not allowed, filter, or mirc. Don't use word boundaries (anywhere in the text is fine). If you need help, try reading this.

Find all occurrences of 4 or more whitespace characters in a row throughout the string.

Replace every . (dot) with a - (hyphen) except when the dot is surrounded by digits. E.g.: .a.b.1.2. should become -a-b-1.2-

Count the number of integers in a given string. Integers are, for example: 1, 2, 65, 2579, etc.

I'd like to know if a text contains words with 4 characters or more which are repeated 3 or more times in the text (anywhere in the text). If so, set one (and only one) backreference for each word.

With regex you can count the number of matches. Can you make it return the number of uppercase consonants (B,C,D,F,..,X,Y,Z) in a given string? E.g.: it should return 3 with the text ABcDeFO!. Note: Only ASCII. We consider Y to be a consonant! Example: the regex /./g will return 3 when run against ...

Only match lines with the text start, unless text end appears prior to start. Note: end may or may not be in the string. Match start line_end; and don't match line_end; start