Regular Expressions 101

1st Alternative(?<=\d)_\d(*SKIP)(*FAIL)

Positive Lookbehind(?<=\d)

\da digit

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

\da digit

(*SKIP)acts like (*PRUNE), but the next unanchored match attempt starts where (*SKIP) was reached instead of at the next subject character

(*FAIL)forces the current match attempt to fail at this position

2nd Alternative_

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

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)_\d(*SKIP)(*FAIL)|_

New

_this_is_a_2_2_replacement_

.