Regular Expressions 101

Explanation
Pro

^start of line

Positive Lookahead(?=[QBNRP ]*K[QBNRP ]*$)

Character Class[QBNRP ]*

*matches any number of characters from the set below:

Qthe literal Q (81₁₀ / 121₈ / 51₁₆) (case sensitive)

Bthe literal B (66₁₀ / 102₈ / 42₁₆) (case sensitive)

Nthe literal N (78₁₀ / 116₈ / 4E₁₆) (case sensitive)

Rthe literal R (82₁₀ / 122₈ / 52₁₆) (case sensitive)

Pthe literal P (80₁₀ / 120₈ / 50₁₆) (case sensitive)

the literal (32₁₀ / 40₈ / 20₁₆)

Kthe literal K (75₁₀ / 113₈ / 4B₁₆) (case sensitive)

Character Class[QBNRP ]*

*matches any number of characters from the set below:

Qthe literal Q (81₁₀ / 121₈ / 51₁₆) (case sensitive)

Bthe literal B (66₁₀ / 102₈ / 42₁₆) (case sensitive)

Nthe literal N (78₁₀ / 116₈ / 4E₁₆) (case sensitive)

Rthe literal R (82₁₀ / 122₈ / 52₁₆) (case sensitive)

Pthe literal P (80₁₀ / 120₈ / 50₁₆) (case sensitive)

the literal (32₁₀ / 40₈ / 20₁₆)

$end of line

Character Class[KQBNRP ]{16}

{16}matches exactly 16 characters from the set below:

Kthe literal K (75₁₀ / 113₈ / 4B₁₆) (case sensitive)

Qthe literal Q (81₁₀ / 121₈ / 51₁₆) (case sensitive)

Bthe literal B (66₁₀ / 102₈ / 42₁₆) (case sensitive)

Nthe literal N (78₁₀ / 116₈ / 4E₁₆) (case sensitive)

Rthe literal R (82₁₀ / 122₈ / 52₁₆) (case sensitive)

Pthe literal P (80₁₀ / 120₈ / 50₁₆) (case sensitive)

the literal (32₁₀ / 40₈ / 20₁₆)

$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

^(?=[QBNRP ]*K[QBNRP ]*$)[KQBNRP ]{16}$

QBNRPQBNRPKQBNRP
KQBNRPQBNRPQBNRP
 KBNRPQBNRPQB RP

KQBNRPQBKRPQBNRP
KQBNRPKQBNRPKQBNRP

QBNRPQBNRPKQBNRP
KQBNRPQBNRPQBNRP
 KBNRPQBNRPQB RP

KQBNRPQBKRPQBNRP
KQBNRPKQBNRPKQBNRP