Regular Expressions 101

^start of line

Condition(?(1)(?|(#\1)|(#))\d+)+

+repeats the group contents below at least once:

Uses the first branch if group 1 matched

If the condition is true, match this branch:(?|(#\1)|(#))\d+

Branch Reset Group(?|(#\1)|(#))

1st Alternative(#\1)

Group 1(#\1)

#the literal # (35₁₀ / 43₈ / 23₁₆)

\1the text saved by group 1

2nd Alternative(#)

Group 1(#)

#the literal # (35₁₀ / 43₈ / 23₁₆)

\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

^(?(1)(?|(#\1)|(#))\d+)+$

New

#123
#12##235
#1234##12###368
#1234##12###368####22235#####723356

##123
#123###456
#123##456##789