use POSIX '_exit';
use File::Find;

my $search_folder = '/some/folder';

find sub {
    return unless -f;
    local @ARGV = $_;
    defined( my $pid = fork ) or die "Cannot fork: $!";
    unless ( $pid ) {
        local $^I = '';
        while ( <> ) {
            s/some text/another text/g;
            print;
            }
        _exit( 0 );
        }
    }, $search_folder;