Beefy Boxes and Bandwidth Generously Provided by pair Networks
Your skill will accomplish
what the force of many cannot

Re: substitution in regular expression

by trizen (Hermit)
on Apr 23, 2014 at 22:15 UTC ( #1083476=note: print w/replies, xml ) Need Help??

in reply to substitution in regular expression

One-line solution: "ABCDEF" =~ /([A-Z]{3})(?{print "$1\n"})(?!)/;

Replies are listed 'Best First'.
Re^2: substitution in regular expression
by aeqr (Novice) on Apr 23, 2014 at 22:27 UTC
    Thanks for the idea, I'll write it down. Just one thing, could you explain the:
    (?{print "$1\n"})(?!)
    I don't understand the question mark before the print block. Also why the (?!) at the end. I noticed that removing it only prints ABC, but I don't understand why. Thank you

      Short explanation: (?{...}) means to execute arbitrary Perl code inside a regular expression, and (?!) makes the regex engine to fail and backtrack, trying to match from the last_pos + 1. When it starts matching ABC, it prints it, fails, backtracks and starts matching from B the next three letters, giving us BCD. The process repeats until the internal regex counter reaches the end of the string.

      I know, I'm really bad at explaining things to humans, but, fortunately, Athanasius explained this better once.

      Please see: Re: RegEx + vs. {1,}

        Thanks a lot! Very well explained actually. It's a nice trick to know.

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1083476]
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others pondering the Monastery: (5)
As of 2018-06-18 04:56 GMT
Find Nodes?
    Voting Booth?
    Should cpanminus be part of the standard Perl release?

    Results (108 votes). Check out past polls.