Regular Expressions 101

Pro

1st Alternative^.{2}(*SKIP)(*FAIL)

^start of line

.{2}any character (except for line terminators), repeated exactly 2 times

(*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[XY](?=[XY_]*$)

Character Class[XY]

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive)

Ythe literal Y (89₁₀ / 131₈ / 59₁₆) (case sensitive)

Positive Lookahead(?=[XY_]*$)

Character Class[XY_]*

*matches any number of characters from the set below:

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive)

Ythe literal Y (89₁₀ / 131₈ / 59₁₆) (case sensitive)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

$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

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25 tokens

^.{2}(*SKIP)(*FAIL)|[XY](?=[XY_]*$)

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