In Perl, what is the difference between use and require for loading a module?

Question

What is the difference between doing use My::Module and require My::Module?

Answer 1

Perl comes with great documentation. Everyone would benefit from reading the entire documentation at least once every few months.

C:\> perldoc -f require

Otherwise require demands that a library file be included if it hasn't already been included. The file is included via the do-FILE mechanism, which is essentially just a variety of eval with the caveat that lexical variables in the invoking script will be invisible to the included code. Has semantics similar to the following subroutine:

... etc. Similarly,

C:\> perldoc -f use

Imports some semantics into the current package from the named module, generally by aliasing certain subroutine or variable names into your package. It is exactly equivalent to

BEGIN { require Module; Module->import( LIST ); }

except that Module must be a bareword.

... etc

There is also the perlfaq entry although I think it is less informative than the above.