Perl’s system function has two modes: taking a single string and passing it to the command shell to allow special characters to be processed taking a list of strings, exec’ing the first and passing the remaining strings as arguments In the first form you have to be careful to escape characters that might have a … Read more
There are problems with the design of smart-matching. The decision of what any given TYPE ~~ TYPE should do is most often unobvious, inconsistent and/or disputed. The idea isn’t to remove smart matching; it’s to fix it. Specifically, ~~ will be greatly simplified, as you can see in a proposal by the 5.18 pumpking. Decisions … Read more
Whenever you can use the name of a variable, you can use a block that evaluates to a reference instead. For example, the following are valid syntax for specifying an array: @NAME # If you have the name e.g. @array @BLOCK # If you have a reference e.g. @{ $ref } This is the “circumfix … Read more
Double quotes use variable expansion. Single quotes don’t In a double quoted string you need to escape certain characters to stop them being interpreted differently. In a single quoted string you don’t (except for a backslash if it is the final character in the string) my $var1 = ‘Hello’; my $var2 = “$var1”; my $var3 … Read more
I think you’re misunderstanding what a fork does. When you successfully fork, you’re creating a subprocess, independent from the process you started with, to continue doing work. Because it’s a separate process, it has its own memory, variables, etc., even though some of these started out as copies from the parent process. So you’re setting … Read more
I mentioned a script a little bit verbose, but which won’t remove any local storage and won’t either clean the CCRC session.dat: nuke_view.pl: you can use it to remove all views from a workstation (which may not be available anymore) cleartool lsview -host myHostname -quick | xargs ccperl nuke_view.pl The -quick option is very important … Read more
Unfortunately, the accepted answer to this question is not yet complete… 🙂 Three (major) classes of parameters Assuming, your ImageMagick version is a recent one, here is an important amendment to it: you should differentiate between 3 major classes of command line parameters: Image Settings Image Operators Image Sequence Operators  These three classes do … Read more
This is a Windows/MS-DOS limitation. According to perldiag: You’re on a system such as MS-DOS that gets confused if you try reading from a deleted (but still opened) file. You have to say -i.bak, or some such. Perl’s -i implementation causes it to delete file1.txt while keeping an open handle to it, then re-create the … Read more
On Read,Invalid encoding otherthan sequence length On Read,Outside of Unicode,Unicode nonchar, orUnicode surrogate On Write,Outside of Unicode,Unicode nonchar, orUnicode surrogate :encoding(UTF-8) Warns and Replaces Warns and Replaces Warns and Replaces :encoding(utf8) Warns and Replaces Accepts Warns and Outputs :utf8 Corrupt scalar Accepts Warns and Outputs (This is the state in Perl 5.26.) Note that :encoding(UTF-8) … Read more
As others have pointed out perl blah.pl asdf works, while blah.pl asdf fails. This is because when you run the perl script directly, Windows realizes it must call perl, and uses the rule perl “%1”, which only passes the script name to perl, not any of the parameters. To fix this, you have to tell … Read more