The substitution is never happening, that's why. And there must be something else you omitted, because as shown, your code does not run because the $NETOBJ variable is not declared anywhere. Removing the "use strict" makes it run, and running it with the -w flag (always use -w and strict!) shows you the problem:

Name "main::NETOBJ" used only once: possible typo at t.pl line 6.
Use of uninitialized value in scalar dereference at t.pl line 6.
Use of uninitialized value in concatenation (.) at t.pl line 6.
[download]

Ok, here's what is happening:

• Because "$$NETOBJ.parameter" is in double quotes, Perl is interpreting $NETOBJ as a variable, and trying to interpolate its value. Because it doesn't have a value, you get an undef value.
• Now, the first "$" in "$$NETOBJ" is also interpolated by perl, trying to interpret it as a dereference to $NETOBJ (this is, if $NETOBJ contained a reference to a scalar value, $$NETOBJ would dereference it and give you the value). Because $NETOBJ is undef, the dereferencing fails too, This produces the "Use of uninitialized value in scalar dereference" error.
• At this point $a contains already ".parameter".
• The substitution is escaped correctly, therefore it looks for the string '$$NETOBJ'. But that string is not there, therefore the substitution doesn't happen, and you get ".parameter" as your final result

The solution if you want the literal string '$$NETOBJ' in $a is to use single quotes instead of double quotes. The single quotes prevent interpolation. Like this:

$a='$$NETOBJ.parameter';
[download]

--ZZamboni

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