perl scripting

perl/wiki

@@ -0,0 +1,100 @@
+-> Perl is weakly typed language.
+
+    $a=10;
+    $b="a";
+    $c=$a.$b;
+    print $c;
+
+    output:
+        10a
+
+
+-> It follows both procedural and object oriented paradigm.
+
+        Ex: Csc01BuildUnit.pm -> Base class = Build.pm
+                ^                               ^
+                |                               |
+            Derived class                   Base class
+
+        With .pm extension is for perl module
+
+-> Perl is interpreted language, but as compare to interpreted language like
+    bash, etc, perl can be compiled to bytecode.
+
+-> Perl can support .pl or .PL extension, but not restricted to these only
+    can also use .pm extension, which used in Tejas Networks.
+
+-> '#!/usr/bin/env perl':
+    Will search for perl in $PATH environment variable from shell and then run from
+    that
+
+    The path mentioned is path for binary 'env' which is used to find 
+    exectuable for perl
+
+    Use command 'which perl' to find the location of perl
+
+-> '#!/usr/bin/perl':
+    This will be used in direct path for perl exectuable( absence of this
+    can lead to error.)
+
+    flags:
+
+    -d: debugging mode(suboption: next, run, step, print, etc).
+            * h: help
+            * run: start execution
+            * next: next line
+            * step: follow function call if there
+            * print: non-nested printing
+            * x: nested printing of objects, data structures, etc
+            * b: set break points
+            * c: continue
+
+    -I Directory: (include directory): Specifies @INC
+        It add specific directories to @INC array
+
+    -w: Shows important warnings
+    -W: Shows all warnings
+    -X: Disable all warnings
+
+    @INC: It is a array of include directory.
+        While running the scripts, we might see this in error logs.
+        This means that some include directories are missing.
+
+-> -e "program": Runs perl script sent in as a program(Interactive mode
+                programming). To run a one liner perl command use -e flag
+
+            perl -e 'print "Hello World\n"'
+            Output: Hello World
+
+-> eval perl: To run multi line perl command use eval perl.
+
+    For example:
+        eval perl
+        @a = ('csc01', 'csc02', 'cef8');
+        print @a, "\n";
+        print "@a\n";
+
+        CTRL+D
+
+-> -t && -T && -U: For security & taint check/warnings.
+    
+    * -T: check for unsecure operation tainting in given perl script
+            and treat them as fatal errors. Stop the scripts
+    * -t: small brother of -T, run the scripts with warnings
+    * -U: Allow unsecure and run scripts without warnings and errors.
+
+-> Comments:
+
+    Begins with '#' symbol.
+    '#' is used for single line comment.
+
+    Multi-line comment is achieved using:
+    =begin 
+     .....
+     comments
+     .....
+    =cut
+
+    exception:
+    '#!/usr/bin/perl' Shabang is not comment. It just tell
+    the bash that its a perl script.