use warnings;
use strict;

checkDir('/usr/tmp', '-w');      #or...
checkDir('/usr/tmp', '-r');

sub checkDir {

  my ($dir, $perm) = @_;

    print "Dir: $dir, Perm: $perm\n";
}
[download]

Dir: /usr/tmp, Perm: -w
Dir: /usr/tmp, Perm: -r
[download]

Bah, read the code!

Ok, better answer - to the actual question:

use warnings;
use strict;

my $testDir = '.';

checkDir($testDir, '-w');
checkDir($testDir, '-r');

sub checkDir {
    my ($dir, $perm) = @_;
    
    if (eval "$perm '$dir'") {
        print "Can $perm $dir\n";
    } else {
        print "Can $perm $dir\n";
    }
}
[download]

Prints:

Can -w .
Can -r .
[download]

This may be a bad idea if the call passes in user supplied text is is not from a trusted place!