Other than the change from "6 identical lines" to "3 identical lines" and the removal of newlines, the OP is a verbatim, blatant plagiarism of this original post:

[Please enter your report here]

The perl program below should print 6 identical lines,
but one of them is different, which appears to be a very
serious bug, perhaps in the optimization of "map".
It appears to not be Solaris-specific.
I also see this on Linux perl 5.6.1.

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

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

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

print map {f1($_)} qw(x y z); print "\n";
print map {f2($_)} qw(x y z); print "\n";
print map {f3($_)} qw(x y z); print "\n";

for my $a (qw(x y z)) { print f1($a) } print "\n";
for my $a (qw(x y z)) { print f2($a) } print "\n";
for my $a (qw(x y z)) { print f3($a) } print "\n";
EOF
xyz
zzz
xyz
xyz
xyz
xyz
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