If AUTOLOAD {} is defined and you call a function that does not exists, AUTOLOAD is called instead.

examples/advanced/autoload.pl
#!/usr/bin/perl
use strict;
use warnings;

f("hello", "world");

AUTOLOAD {
    our $AUTOLOAD;
    print "$AUTOLOAD\n";
    print "@_\n";
}
Output:

main::f
hello world