perl
-i    # edit in place
.bak  # rename original file by appending .bak to filename; print to n
+ew file with original name 
-p    # use a while loop to read each file; print each line (is stored
+ in $_) which you have read (and modified)
e     # excecute code from command line
'     # start of code to be executed (for the default while loop)
$_    # default variable, each line of file
.=    # append the following to yourself ($_) and assign it to you 
"\n"  # string to be appended
'     # end of code

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$_ .= "\n"; is the shorter form of $_ = $_ . "\n";

Check perlrun and look for the explanation for option -i. They have some examples there. -p should be explained in more details, too.

In reply to Re^3: IO::Handles ... any good? by linuxer
in thread IO::Handles ... any good? by blowupp

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