Extract data between square brackets "[]" using Perl
non-greedy, perl, regex
Solution
[Update] In the meantime, I've written a blog post about the specific issue with `.*` I describe below: Why Using .* in Regular Expressions Is Almost Never What You Actually Want
If your identifiers `a1`, `b1` etc. never contain commas or square brackets themselves, you should use a pattern along the lines of the following to avoid backtracking hell:
/\[([^,\]]+),([^,\]]+)\]/
Here's a working example on Regex101.
The issue with greedy quantifiers like `.*` is that you'll very likely consume too much in the beginning so that the regex engine has to do extensive backtracking. Even if you use non-greedy quantifiers, the engine will do more attempts to match than necessary because it'll only consume one character at a time and then try to advance the position in the pattern.
(You could even use atomic groups to make the matching even more performant.)
Problem
I was using a regex for extracting data from curved brackets (or "parentheses") like extracting `a,b` from `(a,b)` as shown below. I have a file in which every line will be like ``` this is the range of values (a1,b1) and [b1|a1] this is the range of values (a2,b2) and [b2|a2] this is the range of values (a3,b3) and [b3|a3] ``` I'm using the following string to extract `a1,b1`, `a2,b2`, etc... ``` @numbers = $_ =~ /\((.*),(.*)\)/ ``` However, if I want to extract the data from square brackets `[]`, how can I do it? For example ``` this is the range of values (a1,b1) and [b1|a1] this is the range of values (a1,b1) and [b2|a2] ``` I need to extract/match only the data in square brackets and not the curved brackets.