in reply to Re^3: $` $' in bash??
in thread $` $' in bash??

I never use English, so I am not sure what it is that you are saying.

You did in the post to which I replied.

What is the reason for using ${^PREMATCH} instead of $PREMATCH?

Quote perlre: "Once Perl sees that you need one of $& , $` , or $' anywhere in the program, it has to provide them for every pattern match. This may substantially slow your program."

${^PREMATCH} and the like are only set on demand (/p), so Perl doesn't need to preemptively populate it whenever you perform a match.