Regular Expressions 101

Pro

^start of line

Condition(?(?=99)99(\.0+)?|([1-9]\d?(\.\d+)?))

Uses the first branch if the lookaround matches

Positive Lookahead(?=99)

99the literal text 99

If the condition is true, match this branch:99(\.0+)?

99the literal text 99

Group 1(\.0+)?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

Otherwise, match this branch:([1-9]\d?(\.\d+)?)

Group 2([1-9]\d?(\.\d+)?)

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\d?optionally matches a digit

Group 3(\.\d+)?

?repeats the group contents below at most 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.

25 tokens

^(?(?=99)99(\.0+)?|([1-9]\d?(\.\d+)?))$

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