in reply to
A little schoolboy math (but my schooldays were a long time ago).

`sub solve{
my( $a, $b, $c, $d ) = @_;
my( $x, $y );
$x = ($b - $a) / ($d - $a - $c + $b);
$y = ($d - $a) * ($b - $a) / ($d - $a - $c + $b) + $a;
return( $x, $y );
}
`

Ok, perhaps more efficiently...

`sub solve{
my( $a, $b, $c, $d ) = @_;
my $x = ($b - $a) / ($d - $a - $c + $b);
my $y = ($d - $a) * $x + $a;
return( $x, $y );
}
`

`formula for line 1: Y = (D - A) * X + A
formula for line 2: Y = (C - B) * X + B
intersection: X and Y coordinates of line1 and line2 are equal ...
(D - A) * X + A = (C - B) * X + B
reduces to => X = (B - A) / (D - A - C + B)
plug X into equation for line 1 gives ...
Y = (D - A) * (B - A) / (D - A - C + B) + A
`