sub findMax {
    my( $f, $x, $step, $eps )= @_;
    while(  1  ) {
        my $y1= $f->( $x );
        $x += $step;         # March forward one more step.
        my $y2= $f->( $x );
        if(  $y2 < $y1  ) {  # Oops, marched past it:
            $step /= -2;     # Turn around, smaller steps.
            if(  $step < $eps  ) {  # Close enough:
                return $x + $step;  # Midpoint of last two steps.
            }
        }
    }
}
my $func= sub { ... };
my $x= findMax( $func, 63.3, 0.1, 0.000001 );
print "Max of ", $func->($x), " at $x.\n";