Question

I was performing a code review for a colleague and he had a regular expression that looked like this:

if ($value =~ /^\d\d\d\d$/) {
    #do stuff
}

I told him he should change it to:

if ($value =~ /^\d{4}$/) {
    #do stuff
}

To which he replied that he preferred the first for readability (I find the second more readable, but that’s a religious debate I’ll save for another day).

My question: is there an actual benefit to one over the other?

Answer 1

They do the exact same thing, so as far as practicality it’s a matter of preference. Is there a tiny performance difference one way or the other? Who knows but it’s surely insignificant.

The quantifiers are more useful (and required) when the pattern length isn’t fixed, for example \d{12,16}, \d{2,}, etc.

I prefer \d{4} which is easier for my brain to parse than \d\d\d\d

Also what if you’re matching a character class rather than a simple digit? [aeiouy0-9]{4} or [aeiouy0-9][aeiouy0-9][aeiouy0-9][aeiouy0-9] ?