use strict;
package junction;
use overload 'eq'=>\&compare;
sub new{
  my $class = shift;
  my $self = {};
  %{$self} = map{$_,1} @_;
  bless $self,$class;
}

sub compare{
  my $self = shift;
  my $string = shift;
  return exists $self->{$string};
}

package main;

my $foo = junction->new("Visa Card","Visa","Visa Check Card");
foreach my $test ("Visa","Vasdfasd","Taco","Visa Check Card") {
  if ($test eq $foo) {
    print "$test is  a Visa!\n";
  }
  else {
    print "$test is NOT a Visa\n";
  }
}

__OUTPUT__
Visa is  a Visa!
Vasdfasd is NOT a Visa
Taco is NOT a Visa
Visa Check Card is  a Visa!