my $my_path = $0;

foreach my $path (split(/:/, $ENV{PATH}))
{
     $my_path = "$path/$0" if (-f "$path/$0");
}

##</code><code>##

my ($called_name) = $0 =~ m#/([^/]+)$#;

{
     no strict;

     &{"mode_$called_name"}() if (defined &{"mode_$called_name"});
}

sub mode_foo
{
     # If program is called as "foo"
}
sub mode_moo
{
     # If program is called as "moo"
}