Some Advice On Eval()-ing code.

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

When I eval code- is it best to do it like this:
Somefile:

{
my $thing_file_dot_inc_needs = 'poopoo';
# Do some more of those.
do file.inc;
}
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Or is there some better way?

Comment on Some Advice On Eval()-ing code. Download Code

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Re: Some Advice On Eval()-ing code. by tall_man (Parson) on Feb 13, 2003 at 05:16 UTC
There are several reasons not to use "do" that way. First, from the perldoc man page: ...code evaluated with do FILENAME doesn't see lexicals in the enclosing scope like eval STRING does. In other words, your "$thing_file_dot_inc_needs" variable won't work. Here's another flaw: ...it does reparse the file every time you call it... It would be better to make the "file.inc" into a module and bring it in with a "use" or "require". Then you are protected from double-inclusion. Lastly, "do" is a heavily-overloaded keyword, also used for loops and subroutines, so it makes the program less clear, IMHO.	[reply]

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Re: Some Advice On Eval()-ing code.
by tall_man (Parson) on Feb 13, 2003 at 05:16 UTC

perldoc

...code evaluated with do FILENAME doesn't see lexicals in the enclosing scope like eval STRING does.

In other words, your "$thing_file_dot_inc_needs" variable won't work. Here's another flaw:

...it does reparse the file every time you call it...

It would be better to make the "file.inc" into a module and bring it in with a "use" or "require". Then you are protected from double-inclusion. Lastly, "do" is a heavily-overloaded keyword, also used for loops and subroutines, so it makes the program less clear, IMHO.

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