perlfaq4: How can I access/change the first N letters of a string?

* changed the title (updated
   + get rid of the /
   + expand the answer to include changes to any part of the string
   + talk about characters, not just letters
   
* the answer now shows the fourth argument to substr()

* the $first_byte variable is now the $first_char variable because
it isn't necessarily a byte.



--- perlfaq.pod 5 Sep 2002 00:48:40 -0000       1.12
+++ perlfaq.pod 4 Nov 2002 20:41:55 -0000
@@ -405,7 +405,7 @@
 
 =item *
 
-How can I access/change the first N letters of a string?
+How can I access or change N characters of a string?
 
 =item *
 
Index: perlfaq4.pod
===================================================================
RCS file: /cvs/public/perlfaq/perlfaq4.pod,v
retrieving revision 1.35
diff -u -d -r1.35 perlfaq4.pod
--- perlfaq4.pod        30 Oct 2002 18:40:34 -0000      1.35
+++ perlfaq4.pod        4 Nov 2002 20:41:57 -0000
@@ -650,23 +650,25 @@
 See the documentation for Text::Autoformat to appreciate its many
 capabilities.
 
-=head2 How can I access/change the first N letters of a string?
-
-There are many ways.  If you just want to grab a copy, use
-substr():
+=head2 How can I access or change N characters of a string?
 
-    $first_byte = substr($a, 0, 1);
+You can access the first characters of a string with substr().
+To get the first character, for example, start at position 0
+and grab the string of length 1.  
 
-If you want to modify part of a string, the simplest way is often to
-use substr() as an lvalue:
 
-    substr($a, 0, 3) = "Tom";
+       $string = "Just another Perl Hacker";
+    $first_char = substr( $string, 0, 1 );  #  'J'
 
-Although those with a pattern matching kind of thought process will
-likely prefer
+To change part of a string, you can use the optional fourth
+argument which is the replacement string.
 
-    $a =~ s/^.../Tom/;
+    substr( $string, 13, 4, "Perl 5.8.0" );
+
+You can also use substr() as an lvalue.
 
+    substr( $string, 13, 4 ) =  "Perl 5.8.0";
+
 =head2 How do I change the Nth occurrence of something?
 
 You have to keep track of N yourself.  For example, let's say you want