my $string = "testing, testing, 123";
my @captured = ($string=~/(testing)/g);
print "captured: $_\n" for @captured;

##</code><code>##

# match lowercase letters commas and space and get as many as possible (greedy)
$string=~/([a-z,\s]+)/; 

# same but non-greedy (stop as soon as you can)
$string=~/([a-z,\s]+?)/;