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Full Discussion: Replacement for eval in Perl??????
Top Forums Shell Programming and Scripting Replacement for eval in Perl?????? Post 302211238 by cbkihong on Thursday 3rd of July 2008 02:00:58 AM
Old 07-03-2008
Quote:
Originally Posted by Annihilannic
There is an eval statement in perl as well.
Please, do not advocate the use of eval unnecessarily because it is a security risk. It should be reserved with tightly controlled commands and in this case this is certainly not tight controlled.

Perl does allow you reference a "variable variable" (a variable whose name is the value held by a variable). That works unless you are in strict mode, in which case an exception will be thrown.

Code:
$num = 60;
$varname = 'num';
print $$varname;    # 60

Even though that works, think about it carefully whether you really need that because not many use cases actually need this.
 

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LEARN ABOUT MOJAVE

observe

observe(n)																observe(n)

__________________________________________________________________________________________________________________________________________________

NAME

       observe - Runtime debugging output in TkCon

SYNOPSIS

       observe command cmdname ?maxlevel?

       observe cdelete cmdname

       observe cinfo cmdname

       observe variable varname operation ?args?

       observe vdelete varname operation

       observe vinfo varname

_________________________________________________________________

DESCRIPTION

       This  command provides runtime debugging output for variables and commands without the need to edit your code.  For variables, the underly-
       ing mechanism uses trace and dump var.  For commands, it renames the observed procedure and uses a  special  wrapper  procedure.   WARNING:
       using this procedure after checkpointing state will result in major problems if you clean state because the renamed (true) commands will be
       lost.

       This procedure is experimental.	Comments are encouraged.

       observe command cmdname ?maxlevel?
	      This will create a wrapper command which prints out (using dump) the call stack to the console.	maxlevel  represents  the  maximum
	      number of levels of the call stack which will be printed (defaults to 4).

       observe cdelete cmdname
	      Removes the wrapper around an observed command.

       observe cinfo cmdname
	      Prints out useless info.

       observe variable varname operation ?args?
	      Currently  a  wrapper  around  trace that uses dump to print out the value of the named variable whenever the specified operation on
	      that variable occurs (must be read, write or unset).

       observe vdelete varname operation
	      Deletes the trace wrapper around the named variable.

       observe vinfo varname
	      Prints out trace info about the named variable.

SEE ALSO

       dump(n), idebug(n), tkcon(1), tkcon(n), tkconrc(5)

KEYWORDS

       Tk, console, debug

COPYRIGHT

       Copyright (c) Jeffrey Hobbs <jeff at hobbs.org>

TkCon									2.5								observe(n)
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