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I need to validate positive currency values under $100, allowing the user to optionally leave out the decimal place. The dollar sign and comma are not needed (or allowed). Another validation component constrains the upper and lower values, so the regex expression only needs to validate 1 or 2 digits, with an optional decimal and 2 more digits.<br />
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These values would match:<br />
<br />
10 <br />
5 <br />
5.00 <br />
10.00<br />
<br />
These values would not match:<br />
<br />
.25 <br />
10.1 <br />
10.255<br />
<br />
What is the optimal regex pattern for this validation?
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I need to validate positive currency values under $100, allowing the user to optionally leave out the decimal place. The dollar sign and comma are not needed (or allowed). Another validation component constrains the upper and lower values, so the regex expression only needs to validate 1 or 2 digits, with an optional decimal and 2 more digits.

These values would match:

10 
5 
5.00 
10.00

These values would not match:

.25 
10.1 
10.255

What is the optimal regex pattern for this validation?

Pseudo currency regex validation

A regular expression ("regex") is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. Regular expression processors are found in several search engines, search and replace dialogs of several word processors and text editors, and in the command lines of text processing utilities, such as sed and AWK. Many programming languages provide regular expression capabilities, some built-in, for example Perl, JavaScript, Ruby, AWK, and Tcl, and others via a standard library, for example .NET languages, Java, Python and C++ (since C++11). Most other languages offer regular expressions via a library.