Metacharacters

Question

"(4{5,6})\1"
I asked about that, and why it matches 10 or 12 fours instead of 5 or 6 fours.
Actually I did not under stand the answer:
/(num) = refers to the group number.
in the above expression we only have the possibility of two group ( 5 fours and 6 fours), so why is the repetition of (5 and 6 fours), can you please explain in details?
thanks.

Answer 1

Hello! The "\1" is the way to refer the anonymous group (4{5,6})
So, the expression "(4{5,6})\1" will match with a pattern like 44444(and again)444444 OR 444444(and again)444444.
I hope to be helpful 😊