Regular Expressions 101

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/
^([1-9]{1,2}){1}(\.[0-9]{1,2})?$
/
^ asserts position at start of the string
1st Capturing Group
([1-9]{1,2}){1}
{1} matches the previous token exactly one time (meaningless quantifier)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data
Match a single character present in the list below
[1-9]
{1,2} matches the previous token between 1 and 2 times, as many times as possible, giving back as needed (greedy)
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
2nd Capturing Group
(\.[0-9]{1,2})?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[0-9]
{1,2} matches the previous token between 1 and 2 times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
$ asserts position at the end of the string
Your regular expression does not match the subject string.

Regular Expression
No Match

/
/

Test String