my $condition = '!-d $someDir';
my $result = checkForDirectory($condition);

sub checkForDirectory
{
    my $condition = shift;
    
    # This is where the problem is. I want to interpolate
    # the text in this variable and use it as my condition.
    # How can I get Perl to DWIM here?
    
    if ($condition)
    {
        doSomethingElse();
    }
}