A dispatch table is a neat way to do that. It is a hash, keyed by your input string, with code references as values.

my %action = (
    go    => sub {
                 # some code
             },
    turn  => \&turn_sub,
    #...
}

while (1) {
    my $act = <>;
    chomp $act;
    # parsing can get fancier here
    exists $action{$act} and $action{$act}->();
}
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After Compline,
Zaxo