You're close. I added strict and warnings, moved the regex into a while loop, added the /g modifier to get all matches, and deleted $2 since you only have one set of capturing parentheses (see perlre). I didn't touch the regex itself, but please note that \w matches "word" characters (alphanumeric plus "_"). If this is sufficient, you could improve the readability of the regex by using it instead of the character classes.

use strict;
use warnings;

my $text = "test1 zzzzzzzzzzzzzzz test2 test3 test4 test5 zzzzzzzzzzzz
+zzz test6 test7 zzzzzzzzzzzzzzz test8 test9 test10";

while( $text =~ /([a-zA-Z0-9]+\s+[z]{15}\s+[a-z0-9]+)/g )
{
    print "string: " . $1 . "!\n";
}
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Output:

string: test1 zzzzzzzzzzzzzzz test2!
string: test5 zzzzzzzzzzzzzzz test6!
string: test7 zzzzzzzzzzzzzzz test8!
[download]