perl 5.003_06: pod/perltrap.pod

Date: Wed, 11 Sep 1996 13:26:18 -0400
From: Gurusamy Sarathy <gsar@engin.umich.edu>
Subject: a perl425 trap

Here's an addition that should be self-explanatory.
[interpolation issues]

Date: Fri, 20 Sep 1996 15:08:33 +0100 (BST)
From: "Joseph S. Myers" <jsm28@hermes.cam.ac.uk>
Subject: Pod typos, pod2man bugs, and miscellaneous installation comments

Here is a patch for various typos and other defects in the Perl
5.003_05 pods, including the pods embedded in library modules.

diff --git a/pod/perltrap.pod b/pod/perltrap.pod
index 984ba3b..bd71ad1 100644 (file)
--- a/pod/perltrap.pod
+++ b/pod/perltrap.pod
@@ -69,13 +69,13 @@ executed.)  See L<perlvar>.
 
 =item *
 
-$<I<digit>> does not refer to fields--it refers to substrings matched by
-the last match pattern.
+$E<lt>I<digit>E<gt> does not refer to fields--it refers to substrings matched
+by the last match pattern.
 
 =item *
 
 The print() statement does not add field and record separators unless
-you set C<$,> and C<$.>.  You can set $OFS and $ORS if you're using
+you set C<$,> and C<$\>.  You can set $OFS and $ORS if you're using
 the English module.
 
 =item *
@@ -103,7 +103,7 @@ basically incompatible with C.)
 The concatenation operator is ".", not the null string.  (Using the
 null string would render C</pat/ /pat/> unparsable, since the third slash
 would be interpreted as a division operator--the tokener is in fact
-slightly context sensitive for operators like "/", "?", and ">".
+slightly context sensitive for operators like "/", "?", and "E<gt>".
 And in fact, "." itself can be the beginning of a number.)
 
 =item *
@@ -295,7 +295,7 @@ you might expect to do not.
 
 =item *
 
-The <FH> construct is not the name of the filehandle, it is a readline
+The E<lt>FHE<gt> construct is not the name of the filehandle, it is a readline
 operation on that handle.  The data read is only assigned to $_ if the
 file read is the sole condition in a while loop:
 
@@ -1176,6 +1176,9 @@ the file.
 
 =head2 Interpolation Traps
 
+Perl4-to-Perl5 traps having to do with how things get interpolated
+within certain expressions, statements, contexts, or whatever.
+
 =over 5
 
 =item * Interpolation
@@ -1189,9 +1192,6 @@ the file.
 
 =item * Interpolation
 
-Perl4-to-Perl5 traps having to do with how things get interpolated
-within certain expressions, statements, contexts, or whatever.
-
 Double-quoted strings may no longer end with an unescaped $ or @.
 
     $foo = "foo$";
@@ -1205,6 +1205,23 @@ Note: perl5 DOES NOT error on the terminating @ in $bar
 
 =item * Interpolation
 
+Perl now sometimes evaluates arbitrary expressions inside braces that occur
+within double quotes (usually when the opening brace is preceded by C<$>
+or C<@>).
+
+    @www = "buz";
+    $foo = "foo";
+    $bar = "bar";
+    sub foo { return "bar" };
+    print "|@{w.w.w}|${main'foo}|";
+
+    # perl4 prints: |@{w.w.w}|foo|
+    # perl5 prints: |buz|bar|
+
+Note that you can C<use strict;> to ward off such trappiness under perl5.
+
+=item * Interpolation
+
 The construct "this is $$x" used to interpolate the pid at that
 point, but now apparently tries to dereference C<$x>.  C<$$> by itself still
 works fine, however.