%hash1 = (
   key1 => "value1",
   key2 => "value2",
   key3 => "value3",
   key4 => "value4",
   key5 => "value5",
);

@array = qw( key3 key4 );


$before = keys %hash1;

foreach (@array){
    delete($hash1{$_});
}

$after = keys %hash1;


print("$before\n");  # 5
print("$after\n");   # 3