Re: Re: understanding eval in HPOJ

[GhodMode]

ummm... definitely not Bash. Actually, exec and eval are fundamental Perl... http://www.perldoc.com/perl5.8.0/pod/func/eval.html http://www.perldoc.com/perl5.8.0/pod/func/exec.html

[Vautrin]

I think the poster may have been referring to the fact that it uses environmental variables.

[ambrus]

It reminds me to some code by which you can run the same script under bash and perl too. One variant of such code is:

           #!/bin/sh -- # -*- perl -*- -p
           eval 'exec perl -wS $0 ${1+"$@"}'
               if $running_under_some_shell;

This has both eval end exec.

The more sophisticated one is:

#! /bin/sh
eval '(exit $?0)' && eval 'PERL_BADLANG=x;PATH="$PATH:.";export PERL_B
+ADLANG\
;exec perl -T -x -S -- "$0" ${1+"$@"};#'if 0;eval 'setenv PERL_BADLANG
+ x\
;setenv PATH "$PATH":.;exec perl -T -x -S -- "$0" $argv:q;#'.q
#!perl -wi.bak
+push@INC,'.';$0=~/(.*)/s;do(index($1,"/")<0?"./$1":$1);die$@if$@__END
+__+if 0
;#Don't touch/remove lines 1--7: http://www.inf.bme.hu/~pts/Magic.Perl
+.Header

(Which runs under csh too).