in reply to Escaping multiple escape chars

If you are working in regular expressions, non-alphanumeric characters are recognised
only if they are preceded by a backslash (\) else it will be treated as:

• perl operators or
• popups an error or
• you will get undesired results.

Lets take a look at your problem.

\ (backslash is a non-alphanumeric character).

\\ (in regular expression, two backslashs are recognised as single backslash)

while trying the below segment...

$txt=~s/\\/\\\\/g;

\\\\ (FOUR backslashs becomes 2 backslashs)

therefore your results will be...

__\\U//__

For your desired output try the below one:

    $txt = ' __\\U//__ ';
    $txt =~s/\\/\\\\\\\\/g;
    print $txt;

[download]

regards
Franklin

Don't put off till tomorrow, what you can do today.

Replies are listed 'Best First'.
Re^2: Escaping multiple escape chars
by JamesNC (Chaplain) on Dec 10, 2005 at 07:14 UTC
    1.frankline unfortunately, your substition gives an incorrect sub for the case \*/, which also appears in the ascii art because it produces an extra '\' where there should be only 1
    Here is the art btw: 
    my $xmas = q%
      __,_,_,___)          _______                                    
+    
    (--| | |             (--/    ),_)        ,_)                      
+    
       | | |  _ ,_,_        |     |_ ,_ ' , _|_,_,_, _  ,             
+    
     __| | | (/_| | (_|     |     | ||  |/_)_| | | |(_|/_)___,        
+    
    (      |___,   ,__|     \____)  |__,           |__,               
+    
                                                                      
+    
                            |                         _...._          
+    
                         \  _  /                    .::o:::::.        
+    
                          (\o/)                    .:::'''':o:.       
+    
                      ---  / \  ---                :o:_    _:::       
+    
                           >*<                     `:}_>()<_{:'       
+    
                          >0<@<                 @    `'//\\'`    @    
+    
                         >>>@<<*              @ #     //  \\     # @  
+    
                        >@>*<0<<<           __#_#____/'____'\____#_#__
+    
                       >*>>@<<<@<<         [__________________________
+]   
                      >@>>0<<<*<<@<         |=_- .-/\ /\ /\ /\--. =_-|
+    
                     >*>>0<<@<<<@<<<        |-_= | \ \\ \\ \\ \ |-_=-|
+    
                    >@>>*<<@<>*<<0<*<       |_=-=| / // // // / |_=-_|
+    
      \*/          >0>>*<<@<>0><<*<@<<      |=_- |`-'`-'`-'`-'  |=_=-|
+    
  ___\\U//___     >*>>@><0<<*>>@><*<0<<     | =_-| o          o |_==_|
+    
  |\\ | | \\|    >@>>0<*<<0>>@<<0<<<*<@<    |=_- | !     (    ! |=-_=|
+    
  | \\| | _(UU)_ >((*))_>0><*<0><@<<<0<*<  _|-,-=| !    ).    ! |-_-=|
+_   
  |\ \| || / //||.*.*.*.|>>@<<*<<@>><0<<@</=-((=_| ! __(:')__ ! |=_==_
+-\  
  |\\_|_|&&_// ||*.*.*.*|_\\db//__     (\_/)-=))-|/^\=^=^^=^=/^\| _=-_
+-_\ 
  """"|'.'.'.|~~|.*.*.*|     ____|_   =('.')=//   ,------------.      
+    
  jgs |'.'.'.|   ^^^^^^|____|>>>>>>|  ( ~~~ )/   (((((((())))))))     
+    
      ~~~~~~~~         '""""`------'  `w---w`     `------------'      
+    %;

    [download]
    I solved the problem by using the suggestion of moving the art into __DATA__ using $xmas = <DATA>; The follow on posts were because I think that this behavior is broken for the case of single versus double quoted strings, but thanks for trying.
[reply]
[d/l]

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