Seems to be a problem with references ...

The map operator receives all the elements of the array (x, y, z) and passes all of them correctly to the function f2:

#! /usr/perl -l

sub f1 {
        my ($f) = @_;
        my @z = ("$f");
        for my $d (@z) {return $d}
}

sub f2 {
        my ($f) = @_;
print "\n*$f*\n"
        for my $d ("$f") {return $d}
}

sub f3 {
        for my $d (@_) {return $d}
}

print map {f1($_)} qw(x y z);
print map {f2($_)} qw(x y z); 
print map {f3($_)} qw(x y z);
[download]

Extrange, is like the function f2, only has been collecting the ref of the $d variable, and when print is going to print the array, it prints the value of the same reference; that is the last 'z' (what's about the scopes!!! arrg)

I have solved the problem using a intermediate variable:

#! /usr/perl -l

sub f1 {
        my ($f) = @_;
        my @z = ("$f");
        for my $d (@z) {return $d}
}

sub f2 {
        my ($f) = @_;
        for my $d ("$f") {my $a=$d; return $a}
}

sub f3 {
        for my $d (@_) {return $d}
}

print map {f1($_)} qw(x y z);
print map {f2($_)} qw(x y z);
print map {f3($_)} qw(x y z);
[download]

cheers