Thank you, Mr. Muskrat. Here is the code & details for you.

use strict;  
use WWW::Mechanize; 
my $mech = WWW::Mechanize->new();   

my $url = "http://www.peoplebank.com/pbank/owa/arcadia.arcadiagroupcat
+egories";

$mech->agent_alias('Mac Safari');
$mech->get($url); 
sleep(1);
$mech->click('');
sleep(2);
# upto here everything seems okay, am getting the page same as from th
+e site.

# In this page, actually a button named "p_next" is there, but I am un
+able to click on this button using the below code.
$mech->click("p_next");  
# The above click will giva an error like, NO clickable input with nam
+e p_next. 
#I tried but unable to solve the Issue, dont know why its not clicking
+, bcoz actually the button is there.
[download]

Hope you can solve it for me. Thanks in advance, Mr. Muskrat.

Yes, the button is present. There are also multiple forms and by default WWW::Mechanize only deals with the first one and the button is not a part of that form.

but i tried it with form_number also, no hope :(