Supposing you have 
my $ref = \"stuff";

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then I know this is a reference to a literal string, and I would be a bit silly to try 
$$ref =~ s/u/i/;
## or even 
$$ref .= " and more stuff";

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But, I have this function that modifies a string, and is designed to modify the actual value: 
sub modify_string{
  my $arg = \shift;

  ## $$arg is modified, no need for the details, eg
  $$arg =~ s/u/i/;
  return $$arg;
}

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so now I can say 
my $string = "stuff";
modify_string( $string );

## or even
my $copy = modify_string( $string );

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Now, some time later I wrote: 
my $new_string = modify_string ( "literal stuff" );

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And to my surprise this works fine! I tested my new code on my ActivePerl 5.6.0 and everything was cool and dandy, so I think, just another of the Perl magic DWIMs.

Then I moved the code to the unix server, also running 5.6.0, it all fell over in a heap. Or I should say, gave the error I expected in the first place: Attempt to modify constant value.

So does anyone (a) know why there is the difference (b) which one is correct and (c) do I need a slapping for writing $arg = \shift; in the first place??

iakobski

In reply to Modifying a reference to a literal string by iakobski

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