From: Mark-Jason Dominus <mjd@plover.com>
Date: Mon, 1 Sep 2003 16:19:20 +0000 (-0400)
Subject: Explain \Q better
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=c83084d1250c5e3fe3236f495fb04a079ccb34d8;p=p5sagit%2Fp5-mst-13.2.git

Explain \Q better
Message-ID: <20030901201920.3929.qmail@plover.com>

p4raw-id: //depot/perl@20997
---

diff --git a/pod/perlfaq6.pod b/pod/perlfaq6.pod
index 9bbf80a..0a134c3 100644
--- a/pod/perlfaq6.pod
+++ b/pod/perlfaq6.pod
@@ -292,14 +292,26 @@ a double-quoted string (see L<perlop> for more details).  Remember
 also that any regex special characters will be acted on unless you
 precede the substitution with \Q.  Here's an example:
 
-    $string = "to die?";
-    $lhs = "die?";
-    $rhs = "sleep, no more";
+    $string = "Placido P. Octopus";
+    $regex  = "P.";
 
-    $string =~ s/\Q$lhs/$rhs/;
-    # $string is now "to sleep no more"
+    $string =~ s/$regex/Polyp/;
+    # $string is now "Polypacido P. Octopus"
 
-Without the \Q, the regex would also spuriously match "di".
+Because C<.> is special in regular expressions, and can match any
+single character, the regex C<P.> here has matched the <Pl> in the
+original string.
+
+To escape the special meaning of C<.>, we use C<\Q>:
+
+    $string = "Placido P. Octopus";
+    $regex  = "P.";
+
+    $string =~ s/\Q$regex/Polyp/;
+    # $string is now "Placido Polyp Octopus"
+
+The use of C<\Q> causes the <.> in the regex to be treated as a
+regular character, so that C<P.> matches a C<P> followed by a dot.
 
 =head2 What is C</o> really for?