Regular Expressions 101

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/
^(\d{3})-(\d{2})-(\d{4})$
/
^ asserts position at start of the string
1st Capturing Group
(\d{3})
\d
matches a digit (equivalent to [0-9])
{3} matches the previous token exactly 3 times
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
2nd Capturing Group
(\d{2})
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 times
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
3rd Capturing Group
(\d{4})
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 times
$ asserts position at the end of the string, or before the line terminator right at the end of the string (if any)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/

Test String