SPUG: Another Eval Question

[Tim Maher/CONSULTIX]

>> Message submitted at: Tue Oct 12 10:25:01 PDT 1999
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According to Asim Jalis:
> 
> Richard A. Puckett II writes:
> > Want to use single quotes here so variables aren't "interpolated".
> > Also want to ditch the ampersand on "length".  FYI, you can check
> > $@ after the eval for possible errors.
> 
> Good point.
> 
> Another question. 
> 
> #!/usr/bin/perl
>   sub hello {
>     my $y; my $x = q{ $y = shift @_; };
>     eval $x;
>     print "y = [$y]\n";
>     print "@ = [$@]\n";
>   }
>   hello(5);
> 
> This prints:
> 
>   y = [5]
>   @ = []
> 
> But replacing "shift @_" with "shift" results in:
> 
>   y = []
>   @ = []

Please read the man pages; for example, "perldoc -f shift" would show you:

shift ARRAY

shift

Shifts the first value of the array off and returns it, shortening the
array by 1 and moving everything down.  If there are no elements in the
array, returns the undefined value.  If ARRAY is omitted, shifts the
@_ array within the lexical scope of subroutines and formats, and the
@ARGV array at file scopes or within the lexical scopes established by
the eval '', BEGIN {}, END {}, and INIT {} constructs.
See also unshift(), push(), and pop().  Shift() and unshift() do the
same thing to the left end of an array that pop() and push() do to the
right end.

> 
> Why is this?
> 
> Asim
> 
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> 
> 

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