Shouldn't that be

eval { goto 'L'.($var+0) }; goto L_default;

L10: print "a";
L9: print "b";
L8: print "c";
L7: print "d";
L6: print "e";
L5: print "f";
L4: print "g";
L3: print "h";
L2: print "i";
L1: print "j";
L_default:

print "\n";
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to preserve the semantics of the original code?

The eval isn't required (unless I missed a subtlety?)

#! perl -sw
use strict;

my $var = 7;

goto 'CASE'.($var+0); die "$var out of range";

CASE10: print "a";
CASE9: print "b";
CASE8: print "c";
CASE7: print "d";
CASE6: print "e";
CASE5: print "f";
CASE4: print "g";
CASE3: print "h";
CASE2: print "i";
CASE1: print "j";

print "\n";

__END__
P:\test>junk
defghij
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The eval is necessary if you want to fully emulate the C semantic of not dieing if there is no matching case. Really, the full-on computed goto method (I should have just written this into my top-level response) is this (I think):

{
eval { goto "CASE$var" } or goto DEFAULT;

    CASE10: print "a";
    CASE9:  print "b";
    CASE8:  print "c";
    CASE7:  print "d";
    CASE6:  print "e";
    CASE5:  print "f";
    CASE4:  print "g";
    CASE3:  print "h";
    CASE2:  print "i";
    CASE1:  print "j";
    DEFAULT: 
}
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Which, admittedly, is not very different from Aristotle's. The only real difference being the outter braces. The purpose of them is to avoid polluting the label name-space. (Also, I prefer the "goto X or goto DEFAULT" over the "goto X; goto DEFAULT" purely for aesthetic reasons. :-D)

I sort of wonder why this isn't given as one of the ways of achieving C-like switch statement behavior in the perl docs? Oh, well... it's probably horribly inefficient or something (apart from just being too C-ish or something).

------------
:Wq
Not an editor command: Wq
[download]

Hmm. I think what your saying is that the eval is necessary to avoid a warning if $var doesn't contain a value for which there is a label defined?

If so, then it still doesn't handle the case where $var is undefined.

That can be handled by using a do BLOCK construct to disable warnings and adding a CASE0:

for my $var ( undef, 1 .. 10, 'fred' ) {
    goto 'CASE' . do{ local $^W; $var + 0 };

    CASE10: print "a";
    CASE9:  print "b";
    CASE8:  print "c";
    CASE7:  print "d";
    CASE6:  print "e";
    CASE5:  print "f";
    CASE4:  print "g";
    CASE3:  print "h";
    CASE2:  print "i";
    CASE1:  print "j";
    print "\n";
    CASE0:
}
[download]

I sort of wonder why this isn't given as one of the ways of achieving C-like switch statement behavior in the perl docs? Oh, well... it's probably horribly inefficient or something (apart from just being to C-ish or something).

C-ish it may be (though that's not a good reason in my book if it is clearer), but inefficient it is not:

P:\test>388915
?> 1..10
Testing for vals [1..10]
               Rate  if_cascade and_cascade     goto_do   goto_eval   
+     goto
if_cascade  11395/s          --         -2%        -11%        -26%   
+     -26%
and_cascade 11627/s          2%          --         -9%        -24%   
+     -25%
goto_do     12845/s         13%         10%          --        -17%   
+     -17%
goto_eval   15389/s         35%         32%         20%          --   
+      -0%
goto        15423/s         35%         33%         20%          0%   
+       --
?>
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Benchmark/results

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---

Examine what is said, not who speaks.

"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon