# create some dummy subroutines
sub test_A {
}
sub test_B {
}

# redefine them as real subs if the conditions
# are right
local *test_A = 
sub {
   my $x = shift;
   # perform test A on $x using data from %data_h
   # if it fails, add an error message and go on to
   # the next list item
} if $condition{'a'} == 1;

local *test_b = 
sub {
   my $x = shift;
   # perform test B on $x using data from %data_h
   # if it fails, add an error message and go on to
   # the next list item
} if $condition{'b'} == 1;

sub do_tests {
   my $to_test = shift;
# depending on what is in the %condition hash,
# these will either be a real subroutine or just a dummy
   test_A($to_test);
   test_B($to_test);
}

foreach (@list) {
   do_tests($_);
   push @passed, $_;
}