Regular Expressions 101

^start of line

Non-Capturing Group(?:\d{50}|(?=.{51})\d+\.\d+)

1st Alternative\d{50}

\d{50}a digit, repeated exactly 50 times

2nd Alternative(?=.{51})\d+\.\d+

Positive Lookahead(?=.{51})

.{51}any character (except for line terminators), repeated exactly 51 times

\d+a digit, repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a digit, repeated at least once

$end of line

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

^(?:\d{50}|(?=.{51})\d+\.\d+)$

12345678901234567890123456789012345678901234567890
12345.123456789012345678901234567890123456789012345