programming-examples/perl/Regular_Expression/grep.pl

#grep value!

@a = (1 .. 10);

@b = grep {$_ > 5} @a;

print join(", ", @b)



#grep with regular rxpression!

print join(" ",(grep {!/^\w{4}$/} (qw(Here are some four letter words.))));

   
    
    
# grep {$_ *= 2}!

@array1 = (1, 1, 1, 1);
@array2 = grep {$_ *= 2} @array1;
print @array1[1];

   
    
#Using grep with the file-test operators.!

     
#!/usr/local/bin/perl 

opendir(CURRDIR, ".") || 
die("Can't open current directory"); 
@filelist = grep (!/^\./, grep(-r, readdir(CURRDIR))); 
closedir(CURRDIR); 
foreach $file (@filelist) { 
    open (CURRFILE, $file) || die ("Can't open input file $file"); 
    while ($line = <CURRFILE>) { 
        if ($line =~ /$ARGV[0]/) { 
            print ("$file:$line"); 
        } 
    } 
    close (CURRFILE); 
} 

   
    
    
#grep function with regular expression!

@a = qw(This is a test);
@b = grep/^\w{4}/, @a;
print "@b";

   
    
#Iterate over matches with foreach and $_ and nested foreach!

#!/usr/bin/perl

use warnings;
use strict;

my $text = "one, two, three, four";

foreach ($text =~ /\b(\w+)\b/g) {
    print "outer: got: $_, matched: $&, extracted: $1 \n";
    foreach (/(\w)/g) {
        print "\tinner: got: $_, matched $&, extracted $1 \n";
    }
}

   


    #Iterate over matches with foreach and $_ and nested while loop!

#!/usr/bin/perl
use warnings;
use strict;

my $text = "one, two, three, four";
while ($text =~ /\b(\w+)\b/g) {
    print "outer: matched: $&, extracted: $1 \n";
    while ($1 =~ /(\w)/g) {
        print "\tinner: matched $&, extracted $1 \n";
    }
}

   
    
 #A program that loops using a pattern.!
  
#!/usr/local/bin/perl 

while ("balata" =~ /.a/g) { 
   $match = $&; 
   print ("$match\n"); 
}