Evaluate an operator given as a string

Hi all.

I'm trying to pass the operators ">=" or "<=" to a subroutine,
and then use it inside an "if" statement.
What changes should i apply to the code below to make it work ?

my_evaluate ( ">=");

sub my_evaluate {
my ($sign) = @_;
my $x = 10;
my $y = 20;
if ($x $sign $y) { # want it to be treated as: if ($x >= $y)
...do something...
}
}


Thanks, Amit.