Perl offers several different ways to include code from one file
into another. Here are the deltas between the various inclusion
1) do $file is like eval `cat $file`, except the former:
1.1: searches @INC and updates %INC.
1.2: bequeaths an *unrelated* lexical scope on the eval’ed code.
2) require $file is like do $file, except the former:
2.1: checks for redundant loading, skipping already loaded files.
2.2: raises an exception on failure to find, compile, or execute $file.
3) require Module is like require “Module.pm”, except the former:
3.1: translates each “::” into your system’s directory separator.
3.2: primes the parser to disambiguate class Module as an indirect object.
4) use Module is like require Module, except the former:
4.1: loads the module at compile time, not run-time.
4.2: imports symbols and semantics from that package to the current one.
In general, you usually want `use’ and a proper Perl module.