Regex Metacharacters
===

most usual regex metacharacters

Representative Metacharacters
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'.' Matches all characters

'[...]' Allow only the characters inside the list

'[^...]' Doesn't allow the characters inside the list

Quantifier Metacharacters
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'?' Do the previous character optional

'-' May does not have several characters of the previous character

'*' Repeat the previous character at least one time

'{ }' Repeat the previous regex or previous characters on the interval between
last and first element - if passed only one element repeat for element-time

Anchors Metacharacters
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'^' Begin of line

'$' End of line

'\b' Start or end with the element - it's depends if passed or begin or end of the line

'\' Remove the special function of the character

'\1' Return **the value, not regex** of a group in the passed position - the count always happens the left to right

'( )' Group a regex, it's necessary with the rearview

(?=RE) / (?!RE) / (?<=RE) / (?<!RE)
---

INPUT: homer simpson | simpson homer

Regex: homer(?= simpson)
Match: **homer** simpson

Regex: homer(?! simpson) 
Match: simpson **homer**

Regex: (?<!simpson )homer
Match: **homer** simpson

Regex: (?<=simpson )homer
Match: simpson **homer**

Obs: The form (? ...) it's supported only for some languages and tools (new metacharacters)