sub check_name {
    return 0;
}


unless (&check_name($app{"first_name"})) { # code } # ,
unless (&check_name($app{"first_name"}) == 1) { # code } # ,
unless (&check_name($app{"first_name"}) eq 1) { # code } # , or
unless (&check_name($app{"first_name"}) eq "1") { # code }

# perl -v
# This is perl, v5.8.4 built for MSWin32-x86-multi-thread
# (with 3 registered patches, see perl -V for more detail)