$ cat long.pl
#!/usr/bin/perl

use strict;
use warnings;

print localtime () . ": Hello from $0 ($$)!\n";
sleep 30;
print localtime () . ": Goodbye from $0 ($$)!\n";
__END__

$ cat fork.pl 
#!/usr/bin/perl

use strict;
use warnings;


print localtime () . ": Hello from the parent ($$)!\n";

my $pid = fork;

die "Fork failed: $!" unless defined $pid;

unless ($pid) {
    print localtime () . ": Hello from the child ($$)!\n";
    exec "./long.pl";  # Some long running process.
    die "Exec failed: $!\n";
}

print localtime () . ": Goodbye from the parent ($$)!\n";
__END__

$ ./fork.pl
Fri Mar 28 13:39:20 2003: Hello from the parent (458)!
Fri Mar 28 13:39:20 2003: Goodbye from the parent (458)!
Fri Mar 28 13:39:20 2003: Hello from the child (459)!
Fri Mar 28 13:39:20 2003: Hello from ./long.pl (459)!
Fri Mar 28 13:39:50 2003: Goodbye from ./long.pl (459)!