$var  = `ls`;
print "\n---\n $var \n---\n ";
The $var will have the output of 'ls' command.

##</code><code>##

$var = system('ls');
print "\n---\n $var \n---\n ";

##</code><code>##

$var = exec('ls');
print "\n---\n $var \n---\n ";