use warnings;
my @list = ();
eval {
    local $SIG{ALRM} = sub { die "SSH timed out" };
    alarm 5; #If after 5 seconds nothing happens, then call SIGALRM
    @list = `ssh machine "ls path"`;
    alarm 0; #Reset
};
if( $@ ) {
    warn "I could not do that: $@";
} else {
    do_something_with( @list );
}