Integrate mainline

[p5sagit/p5-mst-13.2.git] / pod / perlop.pod

diff --git a/pod/perlop.pod b/pod/perlop.pod
index 70fef45..8f2ecde 100644 (file)
--- a/pod/perlop.pod
+++ b/pod/perlop.pod
@@ -300,8 +300,13 @@ to the right argument.
 Binary "<=>" returns -1, 0, or 1 depending on whether the left
 argument is numerically less than, equal to, or greater than the right
 argument.  If your platform supports NaNs (not-a-numbers) as numeric
-values, using them with "<=>" (or any other numeric comparison)
-returns undef.
+values, using them with "<=>" returns undef.  NaN is not "<", "==", ">",
+"<=" or ">=" anything (even NaN), so those 5 return false. NaN != NaN
+returns true, as does NaN != anything else. If your platform doesn't
+support NaNs then NaN is just a string with numeric value 0.
+
+    perl -le '$a = NaN; print "No NaN support here" if $a == $a'
+    perl -le '$a = NaN; print "NaN support here" if $a != $a'
 
 Binary "eq" returns true if the left argument is stringwise equal to
 the right argument.
@@ -1557,19 +1562,19 @@ There are several I/O operators you should know about.
 A string enclosed by backticks (grave accents) first undergoes
 double-quote interpolation.  It is then interpreted as an external
 command, and the output of that command is the value of the
-pseudo-literal, j
-string consisting of all output is returned.  In list context, a
-list of values is returned, one per line of output.  (You can set
-C<$/> to use a different line terminator.)  The command is executed
-each time the pseudo-literal is evaluated.  The status value of the
-command is returned in C<$?> (see L<perlvar> for the interpretation
-of C<$?>).  Unlike in B<csh>, no translation is done on the return
-data--newlines remain newlines.  Unlike in any of the shells, single
-quotes do not hide variable names in the command from interpretation.
-To pass a literal dollar-sign through to the shell you need to hide
-it with a backslash.  The generalized form of backticks is C<qx//>.
-(Because backticks always undergo shell expansion as well, see
-L<perlsec> for security concerns.)
+backtick string, like in a shell.  In scalar context, a single string
+consisting of all output is returned.  In list context, a list of
+values is returned, one per line of output.  (You can set C<$/> to use
+a different line terminator.)  The command is executed each time the
+pseudo-literal is evaluated.  The status value of the command is
+returned in C<$?> (see L<perlvar> for the interpretation of C<$?>).
+Unlike in B<csh>, no translation is done on the return data--newlines
+remain newlines.  Unlike in any of the shells, single quotes do not
+hide variable names in the command from interpretation.  To pass a
+literal dollar-sign through to the shell you need to hide it with a
+backslash.  The generalized form of backticks is C<qx//>.  (Because
+backticks always undergo shell expansion as well, see L<perlsec> for
+security concerns.)
 
 In scalar context, evaluating a filehandle in angle brackets yields
 the next line from that file (the newline, if any, included), or
@@ -1584,7 +1589,7 @@ of a C<while> statement (even if disguised as a C<for(;;)> loop),
 the value is automatically assigned to the global variable $_,
 destroying whatever was there previously.  (This may seem like an
 odd thing to you, but you'll use the construct in almost every Perl
-script you write.)  The $_ variables is not implicitly localized.
+script you write.)  The $_ variable is not implicitly localized.
 You'll have to put a C<local $_;> before the loop if you want that
 to happen.
 
@@ -1729,7 +1734,7 @@ is roughly equivalent to:
 
     open(FOO, "echo *.c | tr -s ' \t\r\f' '\\012\\012\\012\\012'|");
     while (<FOO>) {
-       chop;
+       chomp;
        chmod 0644, $_;
     }