Regular expression examples

[\?&]value=

A URL parameter value in a URL.

[A-Z]:(\\[A-Z0-9_]+)+

An uppercase DOS/Windows path in which (a) is not the root of a drive, and (b) has only letters, numbers, and underscores in its text.

[A-Za-z][A-Za-z0-9_]*

A ColdFusion variable with no qualifier.

([A-Za-z][A-Za-z0-9_]*)(\.[A-Za-z]
[A-Za-z0-9_]*)?

A ColdFusion variable with no more than one qualifier; for example, Form.VarName, but not Form.Image.VarName.

(\+|-)?[1-9][0-9]*

An integer that does not begin with a zero and has an optional sign.

(\+|-)?[1-9][0-9]*(\.[0-9]*)?

A real number.

(\+|-)?[1-9]\.[0-9]*E(\+|-)?[0-9]+

A real number in engineering notation.

a{2,4}

Two to four occurrences of "a": aa, aaa, aaaa.

(ba){3,}

At least three "ba" pairs: bababa, babababa, and so on.