As to return by value, an example:

#!/usr/bin/perl
use 5.016;
use warnings;
use Data::Dumper;

# pass by ref; return by val

my $foo = "abc";

sub subr {
  my $local_foo = shift;            # see Note1, below
  my $local_deref = $$local_foo;
  say " In sub, \$local_deref: $local_deref";
  $local_deref .= " def";
  say "\t  And now, after cat, \$local_deref: $local_deref";
  return $local_deref;
}

my $fooref = \$foo;

my $result = subr($fooref);

say "\t\t Back in main, after subr has returned.";
say "\t\t $result";

[download]

Produces output:

 In sub, $local_deref: abc
          And now, after cat, $local_deref: abc def
                 Back in main, after subr has returned.
                 abc def

[download]

Note1: Had you attempted to -- for example --  print "DEBUG: \$local_foo: $local_foo"; before the deref you would be advised:

 DEBUG: $local_foo: SCALAR(0x169ef64)
... where the hex value (address) will vary with machine, OS or, possibly, whether the butterfly's wings are flapping upward or downward in the jungles or Borneo.


If you didn't program your executable by toggling in binary with a bat-handle switch, it wasn't really programming!

In reply to Re: pass by value vs reference and return by value by ww
in thread pass by value vs reference and return by value by ganeshPerlStarter

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