Re:{3} Regex Grumblings (Variable Interpolation)

But even better, than I tried some deliberate typos, to check for funny things. And guess what, I found something funny!

$_='Some string with $foo and bar';
$bar='bar';
$foo='$bar';

/$bar/ and print "$&\n";
/$foo/ and print "$&\n";
/\Q$fooE/ and print "$&\n";

s/\Q$fooE/XYZ/;
print "$_\n";
[download]

Prints bar twice, and replaces bar by XYZ! This is definitely very strange... is this a bug or what?

Jeroen
"We are not alone"(FZ)
Update: This was run with perl5.6/linux: "This is perl, v5.6.0 built for i386-linux "
(2) grinder I made this typo on purpose.
(3) Thx grinder, things are as they should be now :-)

Comment on Re:{3} Regex Grumblings (Variable Interpolation) Download Code

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Re:x4 Regex Grumblings (Variable Interpolation) by grinder (Bishop) on May 23, 2001 at 16:15 UTC
Don't you mean `/\Q$foo\E/ and print "$&\n"; s/\Q$foo\E/XYZ/;` [download] Using `-w` would have helped you figure it out. Update: oh right, deliberate tyops. Well, now that I've really thought about it... this is what is going on. The line `/\Q$fooE/ and print "$&\n";` [download] given that `$fooE` is not defined is the same thing as `/\Q/ and print "$&\n";` [download] which is the same thing as `// and print "$&\n";` [download] Which is the same thing as finding the same thing as the last successful match. This also applies to the s expression, which is why your bar appears to be magically transmuting itself into XYZ. That's not a bug, that's a feature. -- `g r i n d e r`	[reply] [d/l] [select]

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Re:x4 Regex Grumblings (Variable Interpolation)
by grinder (Bishop) on May 23, 2001 at 16:15 UTC

Don't you mean

  /\Q$foo\E/ and print "$&\n";

  s/\Q$foo\E/XYZ/;
[download]

Using -w would have helped you figure it out.

Update: oh right, deliberate tyops. Well, now that I've really thought about it... this is what is going on. The line

/\Q$fooE/ and print "$&\n";
[download]

given that $fooE is not defined is the same thing as

/\Q/ and print "$&\n";
[download]

which is the same thing as

// and print "$&\n";
[download]

Which is the same thing as finding the same thing as the last successful match. This also applies to the s expression, which is why your bar appears to be magically transmuting itself into XYZ.

That's not a bug, that's a feature.

--
g r i n d e r

[reply]
[d/l]
[select]