First, always use

use strict;
use warnings;
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• You're comparing strings with the numerical comparison operator. Use eq instead of ==.

• Well, you would be if you had actually populated your hash properly. You only assign one element to your hash, a reference to another anonymous hash. You need to assign a list of key-value pairs. Change = { } to = ( ).

• Iterating through the entire hash defies the purpose of using a hash, especially when you know the key you want to locate.

• Perl doesn't have a break keyword. C's break is called last in Perl.

• Code that comes after a return doesn't get executed. That break is never reached.

Fix:

use strict;
use warnings;

my %dbase = (
   apple   => "fruit",
   brinjal => "vegetable",
   coffee  => "beverage",
);

sub validate {
   my ($usr, $pwd) = @_;
   return exists($dbase{$usr}) && $dbase{$usr} eq $pwd;
}

my @info = ( "lemon", "juice" );
my $result = validate(@info) ? "ok" : "forbidden";
print "$result\n";
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