System command problem in perl

vr786 has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks, i have written a small script to remove and add comments in a file, problem comes here is:removing comments is working but adding comments is not working, if i will run the same code separately (through command line , manually) working fine , can any one help me.

My input file test.txt consists test test test\n testing testing\n test\n testing\n

!/usr/bin/perl -w
use strict;
use warnings;
my $cmd;
my $cmd1;
$cmd = system("perl -pi -e 's/#//' test.txt"); # removing comments wor
+king
$cmd1 = system("perl -pi -e 's/(?=.*\btest\b)/#/' test.txt"); #Adding 
+#'s is not working
print "$cmd \n";
print "$cmd1\n";
[download]

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Re: System command problem in perl by jwkrahn (Abbot) on Nov 26, 2010 at 15:19 UTC
You don't need to run perl through system, you can do that directly in perl: `#!/usr/bin/perl use strict; use warnings; { local ( $^I, @ARGV ) = ( '', 'test.txt' ); while ( <> ) { s/#//; print; } } { local ( $^I, @ARGV ) = ( '', 'test.txt' ); while ( <> ) { s/(?=.*\btest\b)/#/; print; } }` [download]	[reply] [d/l]
Re: System command problem in perl by mjscott2702 (Pilgrim) on Nov 26, 2010 at 12:50 UTC
That shouldn't even compile/run: Global symbol "$cmd1" requires explicit package name at try4.pl line 3. Global symbol "$cmd1" requires explicit package name at try4.pl line 4. Global symbol "$cmd" requires explicit package name at try4.pl line 5. Global symbol "$cmd1" requires explicit package name at try4.pl line 6. Apart from not using "my" to declare your variables, notice that you reference $cmd, which isn't actuallly declared/assigned to anywhere.	[reply]
Re: System command problem in perl by Anonymous Monk on Nov 26, 2010 at 12:01 UTC
1) don't use the shell `my @args = ( $^X, qw' -pi -e ', $perlprogram, 'test.txt' ); system {$args[0]} @args;` [download] 2) What is your expected output? Where do you want to add # that isn't happening	[reply] [d/l]
Re^2: System command problem in perl by tod222 (Pilgrim) on Nov 26, 2010 at 21:07 UTC
system {$args[0]} @args; No, don't use system just to run perl when the task can be simply done in a single Perl script. See jwkrahn's response below.	[reply]