edit_file reads a whole file into $_, calls its code block argument and
writes $_ back out the file. These groups are equivalent operations:

perl -0777 -pi -e 's/foo/bar/g' filename

use File::Slurp qw( edit_file ) ;

edit_file { s/foo/bar/g } 'filename' ;

edit_file sub { s/foo/bar/g }, 'filename' ;

edit_file \&replace_foo, 'filename' ;
sub replace_foo { s/foo/bar/g }

edit_file_lines reads a whole file and puts each line into $_, calls its
code block argument and writes each $_ back out the file. These groups are
equivalent operations:

perl -pi -e '$_ = "" if /foo/' filename

use File::Slurp qw( edit_file_lines ) ;

edit_file_lines { $_ = '' if /foo/ } 'filename' ;

edit_file_lines sub { $_ = '' if /foo/ }, 'filename' ;

edit_file \&delete_foo, 'filename' ;
sub delete_foo { $_ = '' if /foo/ }

So now when someone asks for a simple way to modify a file from inside
Perl, you have an easy answer to give them.

The design philosophy of T::S is total isolation of data logic from the
template itself. A template designer can work independently from a coder
who works on the data. Also this give more flexibility you can mix and
match different templates with different data trees without rewriting
either. All the common idioms are supported including nested data and
templates, include files, loops, conditionals, etc. You can also customize behavior with code callbacks in the data. The cookbook script
in extras/ will get you started with all of the idioms. And with the
compiled templates you now get the fastest rendering.

Have the appropriate amount of fun.