As the others have pointed out the shell doesn't work like that. A possible workaround is to alias the output of the program to a command:

#!/usr/bin/perl -w

use strict;

my $dir = '/usr/bin';

if (chdir $dir) {
    print $dir;
}
else {
    print STDERR "Couldn't cd to $dir\n";
    print '.';
}

__END__

Then in your shell set an alias:
    alias mycd='cd `perl mycd.pl`'
[download]

--
John.