Searching for a string
------------------------------

#!/usr/bin/perl -w

$exp = "This is a string";

if ($exp =~ /This/) {
        print ("String Matches!\n");
}


Searching for a string using case insensitive
--------------------------------------------------------------

#!/usr/bin/perl -w

$exp = "This is a string";

if ($exp =~ /tHis/i) {
        print ("String Matches!\n");
}


Searching for a digit
----------------------------

#!/usr/bin/perl -w

$exp = "This is 8 string";

if ($exp =~ /\d/) {
        print ("String Matches!\n");
}

Searching for 2 digits
-----------------------------

#!/usr/bin/perl -w

$exp = "This is 88 string";

if ($exp =~ /\d\d/) {
        print ("String Matches!\n");
}


Searching for whitespaces
-------------------------------------

#!/usr/bin/perl -w

$exp = "This is string";

if ($exp =~ /\s/) {
        print ("String Matches!\n");
}


Searching for a string that begins with a pattern
----------------------------------------------------------

#!/usr/bin/perl -w

$exp = "This is string";

if ($exp =~ /^This/) {
        print ("String Matches!\n");
}


Searching for a string that ends with a pattern
----------------------------------------------------------------

#!/usr/bin/perl -w

$exp = "This is string";

if ($exp =~ /string$/) {
        print ("String Matches!\n");
}


Search for a digit with white space in front and after it.
--------------------------------------------------------------------------

#!/usr/bin/perl -w

$exp = "This 1 is string";

if ($exp =~ /\s\d\s/) {
        print ("String Matches!\n");
}


Search for a blank line
------------------------------

This is usefull  to check for blank lines in a file. For that, instead of $exp variable you will need an array that will contain every line from that file.

#!/usr/bin/perl -w

$exp = "";

if ($exp =~ /^$/) {
        print ("String Matches!\n");
}

 
Replace a pattern
------------------------

#!/usr/bin/perl -w

$exp = "This is a string";

if ($exp =~ s/This is/Test/) {
        print ("$exp\n");
}