lanx@lanx-1005HA:/tmp$ cat Weird.pm 
package Weird;

use Carp qw/cluck/;

sub tst {
    cluck "cluck tst entered";

    print "\nnormal output in tst()...\n";
    # ...
}

sub tst2 {
    tst();
}

warn "\n--- using Weird.pm\n";
tst2();                   # line 17 - executed at "use Weird" time


sub import {
    warn "\n--- importing from Weird.pm\n";
    tst2();               # line 22 - executed at Weird::import() time
}

1;