use strict;
use warnings;
use 5.012;

sub do_stuff {
    glob "dir1/f*";
}

for my $i (1..10) {
    print "$i: ";

    if (my $x = do_stuff()) {
        print "\t$x";
    }

    print "\n";
}

--output:--
1: 	dir1/f1
2: 	dir1/f2
3: 
4: 	dir1/f1
5: 	dir1/f2
6: 
7: 	dir1/f1
8: 	dir1/f2
9: 
10: 	dir1/f1