Return string that starts and ends with specific characters

gilthoniel has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Return string that starts and ends with specific characters by Anonymous Monk on Jun 02, 2016 at 16:46 UTC
`#!/usr/bin/perl # http://perlmonks.org/?node_id=1164776 use strict; use warnings; my @answer; 'asdfgfhjkl' =~ /f.*j(?{push @answer, $&})^/; print "$_\n" for @answer;` [download]	[reply] [d/l]
Re^2: Return string that starts and ends with specific characters by LanX (Saint) on Jun 02, 2016 at 16:53 UTC
I had basically the same idea, but tried `\0` to force the backtracking. (which didn't work) Why and how does `^` work? Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply] [d/l] [select]
Re^3: Return string that starts and ends with specific characters by Eily (Monsignor) on Jun 02, 2016 at 16:59 UTC
It works with `(?=\0)` so I'd say it comes from zero-width assertions preventing optimization. Edit : In this special case (single word without a j at the end) it also works with \b	[reply] [d/l]
Re^4: Return string that starts and ends with specific characters by AnomalousMonk (Archbishop) on Jun 02, 2016 at 17:42 UTC
Re^5: Return string that starts and ends with specific characters by Eily (Monsignor) on Jun 02, 2016 at 18:42 UTC
Re^4: Return string that starts and ends with specific characters by Anonymous Monk on Jun 02, 2016 at 17:02 UTC
Re^3: Return string that starts and ends with specific characters by Anonymous Monk on Jun 02, 2016 at 16:55 UTC
I think regex is smart enough to detect no \0 but not ^	[reply]
Re^4: Return string that starts and ends with specific characters by LanX (Saint) on Jun 03, 2016 at 00:26 UTC
Re^5: Return string that starts and ends with specific characters by LanX (Saint) on Aug 19, 2016 at 21:56 UTC
Re: Return string that starts and ends with specific characters by Anonymous Monk on Jun 02, 2016 at 16:49 UTC
`#!/usr/bin/perl # http://perlmonks.org/?node_id=1164776 use strict; use warnings; print "$1\n" while 'asdfgfhjkl' =~ /(?=(f.*j))/g` [download]	[reply] [d/l]
Re^2: Return string that starts and ends with specific characters by Eily (Monsignor) on Jun 02, 2016 at 16:56 UTC
The previous one works not only with multiple 'f's but also with multiple 'j's, this one will always match up to the rightmost 'j'.	[reply]
Re^3: Return string that starts and ends with specific characters by Anonymous Monk on Jun 02, 2016 at 16:58 UTC
Yep. I was not sure what his actual requirements were, so I showed both.	[reply]
Re^3: Return string that starts and ends with specific characters by gilthoniel (Novice) on Jun 02, 2016 at 17:24 UTC
Thanks this is great! How would I get it to print only to the leftmost j?	[reply]
Re^4: Return string that starts and ends with specific characters by gilthoniel (Novice) on Jun 02, 2016 at 17:26 UTC
Re^5: Return string that starts and ends with specific characters by Anonymous Monk on Jun 02, 2016 at 17:34 UTC