How can I find the location of a regex match in Perl?

Question

I need to write a function that receives a string and a regex. I need to check if there is a match and return the start and end location of a match. (The regex was already compiled by qr//.)

The function might also receive a "global" flag and then I need to return the (start,end) pairs of all the matches.

I cannot change the regex, not even add () around it as the user might use () and 1. Maybe I can use (?:).

Example: given "ababab" and the regex qr/ab/, in the global case I need to get back 3 pairs of (start, end).

Answer 1

The built-in variables @- and @+ hold the start and end positions, respectively, of the last successful match. $-[0] and $+[0] correspond to entire pattern, while $-[N] and $+[N] correspond to the $N ($1, $2, etc.) submatches.