Can not run ack after installing it using MacPorts
MacPorts, by default, installs into /opt/local/, judging by the screen shot ack should be in /opt/local/perl/p5-app-ack/ if you used the default install path. Make sure that path is in your $PATH environment variable.

To add it to your path edit your shell config file (probably ~/.profile or ~/.bashrc) and add or modify the following line.
export PATH="$PATH":/opt/local/perl/p5-app-ack

I don't use MacPorts for ack, I install it manually with the following command from the ack install page.

curl http://betterthangrep.com/ack-standalone &gt; ~/bin/ack &amp;&amp; chmod 0755 !#:3

This will install ack into the $HOME/bin/ folder as a single large perl file and I did not have to modify my $PATH variable.