Re^2: How to match last character of string, even if it happens to be a newline?

This reduces the degrees of freedom of the ^ $ . operators

Maybe that hints at the following inconsistency I see with the "the end of the line (or before newline at the end)" rule?

Example

print('String: a\nb\nc\n' . "\n");
$text_1 = "a\nb\nc\n";
$text_1 =~ s@(\n)$@@s;
print("----------\n>" . $1 . "<\n");
print("----------\n>" . $text_1 . "<\n");
[download]

Gives:

String: a\nb\nc\n
----------
>
<
----------
>a
b
c<
[download]

In this case, the $ behaved like \z. Or another way to say it, in this case explicit \n matches where dot with s mod doesn't.

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Re^3: How to match last character of string, even if it happens to be a newline? by AnomalousMonk (Archbishop) on May 12, 2019 at 16:56 UTC
... in this case explicit \n matches where dot with s mod doesn't. That's because `\n$` requires a match with newline, but `.$` allows the leftmost position of a match with dot (with `/s`) to be before the newline. Dot will match newline in the presence of `$` if it is the only match available: `c:\@Work\Perl\monks>perl -wMstrict -le "use Data::Dump qw(pp); ;; for my $s (qq{yz}, qq{yz\n}, qq{\n}) { $s =~ m{ (.) $ }xms; printf qq{in %s matched %s \n}, pp($s), pp($1); } " in "yz" matched "z" in "yz\n" matched "z" in "\n" matched "\n"` [download] (The `/m` modifier makes no difference in these example strings.) The thing to remember about regular expressions is that there are a lot of things to remember about regular expressions. If you have a chance to reduce the amount of stuff to remember, even if only by a little, take it. That's why I advise (per TheDamian's regex PBPs) using `\A \z \Z` for all your start- and end-of-string anchoring needs, and using `^ $` only for embedded newline matching. ... inconsistency ... For me, it's not so much inconsistency as mind-boggling complexity. And again, I come back to the point that if you can reduce the complexity of what you're dealing with even a little, you're ahead of the game. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]

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Re^3: How to match last character of string, even if it happens to be a newline?
by AnomalousMonk (Archbishop) on May 12, 2019 at 16:56 UTC

... in this case explicit \n matches where dot with s mod doesn't.

That's because \n$ requires a match with newline, but .$ allows the leftmost position of a match with dot (with /s) to be before the newline. Dot will match newline in the presence of $ if it is the only match available:

c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(pp);
 ;;
 for my $s (qq{yz}, qq{yz\n}, qq{\n}) {
   $s =~ m{ (.) $ }xms;
   printf qq{in %s matched %s \n}, pp($s), pp($1);
   }
"
in "yz" matched "z"
in "yz\n" matched "z"
in "\n" matched "\n"
[download]

/m

The thing to remember about regular expressions is that there are a lot of things to remember about regular expressions. If you have a chance to reduce the amount of stuff to remember, even if only by a little, take it. That's why I advise (per TheDamian's regex PBPs) using \A \z \Z for all your start- and end-of-string anchoring needs, and using ^ $ only for embedded newline matching.

... inconsistency ...

For me, it's not so much inconsistency as mind-boggling complexity. And again, I come back to the point that if you can reduce the complexity of what you're dealing with even a little, you're ahead of the game.

Give a man a fish: <%-{-{-{-<

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