in reply to Regexes and backslashes

my $text = 'Goodbye\; Good luck\, and thanks for all the fish!\\n\\n';

$text =~ s{ \\ ([^n]) }
                {$1}xmsg;

print "-->$text<--";

--output:--
-->Goodbye; Good luck, and thanks for all the fish!\n\n<--

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Re^2: Regexes and backslashes
by oko1 (Deacon) on Feb 16, 2011 at 05:01 UTC

    Oh, dear. I guess I'm extra awful at explaining what I mean tonight. Pity; I suppose the only thing left is to shoot myself and get it over with. :)

    Your example does indeed result in the above output - but that's not what I'm looking for. I would like for the escaped semicolons to be converted to non-escaped semicolons; for escaped commas to be converted to non-escaped commas; and for escaped newlines to be converted to actual newlines. Metacharacters, not literal '\n's. Ones that actually result in newlines being produced on the screen when a line is printed - i.e.,

    Line 1:Goodbye; Good luck, and thanks for all the fish!
    Line 2: 

    and NOT

    Line 1:Goodbye; Good luck, and thanks for all the fish!\n\n

    (I'm not trying to come across as being snarky; I'm just trying to make *sure* that I'm getting across what I mean, since I've obviously failed to do so before now.) 

    -- 
Education is not the filling of a pail, but the lighting of a fire.
 -- W. B. Yeats
[reply]

      OK, how about this one. It's a little bit klunky in its use of a conversion hash, but the hash can easily be expanded as needed. 

      >perl -wMstrict -le
"$_ = 'Goodbye\; Good luck\, and thanks for all the fish!\n\n';
 my %conv = ( ',' => ',',  ';' => ';',  n => qq{\n} );
 print qq{[[$_]]};
 s{ \\([,;n]) }{$conv{$1}}xmsg;
 print qq{[[$_]]};;
"
[[Goodbye\; Good luck\, and thanks for all the fish!\n\n]]
[[Goodbye; Good luck, and thanks for all the fish!

]]

      [download]
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[d/l]

        Heh. Yeah, we could even in-line it: 

        s|\\([,;n])|${{',',',',';',';',n=>"\n"}}{$1}|g;

        [download]

        Nicely confusing. :)

        I guess there really is no way to make this work with a simple char class replacement, though. Oh well. 

        -- 
Education is not the filling of a pail, but the lighting of a fire.
 -- W. B. Yeats
[reply]
[d/l]

      Aye, this does make it more clear, although I already understood what you meant in the end.

      The problem of course was your extra backslashes in the original string confused your intent.

      $_ = 'Goodbye\; Good luck\, and thanks for all the fish!\\n\\n';

      [download]

      Being synonymous with and more simply stated as

      $_ = 'Goodbye\; Good luck\, and thanks for all the fish!\n\n';

      [download]

      I certainly understand your beef with evaling, but given you know the content of the eval to a certainty, I don't believe there is any security risk. Would be interested if proven wrong there though.

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