programming-examples/perl/Regular_Expression/Escape.pl

#A word-count program that handles multiple spaces and tabs between words.!

#!/usr/local/bin/perl 

$wordcount = 0; 
$line = <STDIN>; 
while ($line ne "") { 
   chop ($line); 
   @words = split(/[\t ]+/, $line); 
   $wordcount += @words; 
   $line = <STDIN>; 
} 
print ("Total number of words: $wordcount\n"); 

   
    
#Escape Sequences for Special Characters!

To include a backslash in a pattern, specify two backslashes: 
/\\+/ 

This pattern tests for one or more occurrences of \ in a string. 

   
    
#Escape sequences, \n and \t!

while(<DATA>){
    print if s/\n/\t/;
}
__DATA__
    AA AA AQA 101

  
   
    
# Match the new line character!

$_ = "This text\nhas multiple lines.";
s/^/BOL/g;
s/$/EOL/g;
print;

   
    
    
    
  #Skip blank lines and comments!

#!/usr/bin/perl

use warnings;
use strict;

while (<>) {
    chomp;   # strip trailing linefeed from $_
    next if /^(\s*(#.*)?)?$/;   # skip blank lines and comments
    print "Got: $_ \n";
}

   
    
    
  #Match multiline patterns?!

    #!/usr/local/bin/perl -w
    use strict;

    $/ = "";   # Paragraph mode

    while(<>) {
      print $1 if /(lines.*\n.*spaces)/s;
    }

   
    
    #Multiplies every integer in a file by 2!

#!/usr/local/bin/perl 

$count = 0; 
while ($ARGV[$count] ne "") { 
   open (FILE, "$ARGV[$count]"); 
   @file = <FILE>; 
   $linenum = 0; 
   while ($file[$linenum] ne "") { 
      $file[$linenum] =~ s/\d+/$& * 2/eg; 
      $linenum++; 
   } 
   close (FILE); 
   open (FILE, ">$ARGV[$count]"); 
   print FILE (@file); 
   close (FILE); 
   $count++; 
}