Linux: Perl - 3

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-Perl control structures:
-    if (expr) {...}
    unless (expr) {...}
-    if (expr) {...} else {...}
-    if (expr) {...} elsif {...} .. else {...}
-    foreach|for var (list) {...}
-    foreach|for (expr1; expr2; expr3) {...}
-    while (expr) {...}
-    until (expr) {...}

-useful functions/expressions:
-    my        - limits scope of a variable
-    die        - sends its argument to stderr and aborts program
-    chomp        - removes trailing newlines
-    say        - prints with a newline
-    print        - prints output on stdout
-    open        - opens a file
-    sort        - returns elements of an array in order
-    reverse        - returns elements of an array in reverse order
-    $!        - last system error
-    @ARGV        - array holding the arguments from the cmdline
-    %ENV        - env variables of the shell that called perl
-    split        - divides a string into substrings
- shift, push, pop, slice - array functions
-subroutines are distinct function blocks apart from the main program.
-subroutines can be called by other programs.
-this keeps the program structure modular.
-variables defined in the main prog are available to the subroutines.
-variables defined in the subroutine hv local scope by default.
-subs are defined by sub keyword and a name, {}
-eg: sub asub{..}
-they are called by their name and ()
-eg: asub ()
-params passed to a subroutine are listed in an array @_ and elements in @_ are $_
-cpan is the repository for perl docs, faqs and modules.
-perl modules come as tar files.
-in the module, first follow the 'readme' file.
-then create the config by running 'perl Makefile.PL'
-then run the 'make' on the Makefile just created to create the pkg.
-then run the 'make test' to test the module works.
-then run the 'make install' as root to install the module.
-post install, you can query perldoc to review the documentation.