sub mapfirst {
    my( $sub )= shift( @_ );
    &$sub( map { $_->[0] } @_ );
#          ^^^^^^^^^^^^^^^^^^ Here is the selection code
}
my @a= ( 1..3 );
my @b= ( 4..6 );
my @c= ( 7..9 );
sub addten { $_ += 10  for @_ }
mapfirst( \&addten, \@a, \@b, \@c );
mapfirst( sub { print "@_\n" }, \@a, \@b, \@c );