from perldoc -f use:

    use Module VERSION LIST
    use Module VERSION
    use Module LIST
    use Module
    use VERSION
            Imports some semantics into the current package from the n
+amed
            module, generally by aliasing certain subroutine or variab
+le
            names into your package. It is exactly equivalent to

                BEGIN { require Module; import Module LIST; }

            except that Module *must* be a bareword.
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and from perldoc -f require:

            If EXPR is a bareword, the require assumes a ".pm" extensi
+on and
            replaces "::" with "/" in the filename for you, to make it
+ easy
            to load standard modules. This form of loading of modules 
+does
            not risk altering your namespace.

            In other words, if you try this:

                    require Foo::Bar;    # a splendid bareword

            The require function will actually look for the "Foo/Bar.p
+m"
            file in the directories specified in the @INC array.

            But if you try this:

                    $class = 'Foo::Bar';
                    require $class;      # $class is not a bareword
                #or
                    require "Foo::Bar";  # not a bareword because of t
+he ""

            The require function will look for the "Foo::Bar" file in 
+the
            @INC array and will complain about not finding "Foo::Bar" 
+there.
            In this case you can do:

                    eval "require $class";
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so BEGIN{ my $var= 'CGI'; eval "require $var"; $var->import(); } should work.

~Particle *accelerates*