$ cat Foo.pm
package Foo;
require Exporter;
our @ISA = qw( Exporter );
our @EXPORT_OK = qw( saySomething );

sub saySomething {
    print "Foo!\n";
}

# Special package initialization stuff
print "Special FOO.PM initialization complete!\n";

1;

$ cat T.pl
#!env perl
use lib '.';
use Foo qw( saySomething );

print "Begin\n";
saySomething();
print "End\n";

$ perl t.pl
Special FOO.PM initialization complete!
Begin
Foo!
End