use strict;
use warnings;
use File::Next;

my $find_this = sub {
    my ($starting_points, $target) = @_;
    my $ref_sub = File::Next::files( "$starting_points" );
    while ( my @files = $ref_sub->()  ) {
    return @files if $files[1] =~ $target;
    }
};

my @files = &$find_this( "/tmp/dir1",  "file3.txt" );
print "@files\n";