Regular Expressions 101

^start of line

Negative Lookahead(?![AM]\d{4})

Character Class[AM]

Athe literal A (65₁₀ / 101₈ / 41₁₆) (case sensitive)

Mthe literal M (77₁₀ / 115₈ / 4D₁₆) (case sensitive)

\d{4}a digit, repeated exactly 4 times

.*any character (except for line terminators), repeated any number of times

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(?![AM]\d{4}).*

New

A1234
M3232
M3425435324
MM3453
JHLKJGA1234
string with nothing