Perl is not really pass-by value - the stuff in @_ are (aliases to) the actual variables you pass in, not copies:

sub foo_ize {
  for my $val (@_) {
    $val =~ s!bar!foo!gi;
  };
};

my @arr = qw( baz bar baz BarBar );
foo_ize @arr;
print join ",", @arr;
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The "pass by value" comes into effect once you employ the standard practice of copying your parameters:

sub foo_ize_val {
  my @args = @_;
  map { s!foo!bar!ig; $_ } @args;
};

my @arr = qw( baz bar baz BarBar );
foo_ize @arr;
print join ",", @arr;
@arr = foo_ize @arr;
print join ",", @arr;
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