I am trying to write a command parser which is like cisco CLI.(still in basic level). Here is the snippet of the code. 
use warnings;
use Carp;
use Parse::RecDescent;
$|=1;
my $GlobalConfigMode=q(
 Interface: ('fa' |'gigabit' |'atm') module '/' slot {print "SUCCESS"}
+ 
 module: /\d+/<commit>|<error?:invalid module >
 slot:/\d+/<commit> |<error?: error near slot: >
 );
my $parser= new Parse::RecDescent($GlobalConfigMode) or croak "Could n
+ot create command parser" ;
while(<DATA>){
    chomp;
    if($parser->Interface($_)){
            print "$_ \t success\n" ;
            
        }
        else {
            print "$_ Command not found\n";
        }
        
print"------------------\n";

}


__DATA__
fa 0/1
atm 0/1
gigabit 0/1
fastethernet co 
gigabit 01111
fa 0/1 enable
gigabit 0/1 disable
fastethenet asdf

[download]
Problem here is that I get different result if I take this value from STDIN .(ie changing the <DATA> in while loop to <STDIN>) Though basic parsing works, if I give additional characters it does not complain.(ie if I give input as <fa 0/1 junkcharcctrasdfadsf> from commandline)

I am wondering is there any difference in these two mode of inputs ?
Expected result is
1. fa 0/1 --> success
2. fa 0/1 enable -> fail
3. gigabit 0/1 --> success.
4. gigabit 0/1 enable/remove --> fail

In reply to Difference between Inputs taken from __DATA__ and STDIN. by raghrao

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