Programming :: Delete Multiple Lines In A File Using Perl?

I have a file looks like the following:

digraph topology
{
"192.168.3.254" -> "10.1.1.11"[label="1.000", style=solid];
"192.168.3.254" -> "10.1.1.12"[label="1.000", style=solid];

[code]...

Order of these lines are random... So I cannot delete line #19, for example... And you can see that top four lines I want to delete are pairs. So there might be some clever way to detect the lines, if a line has both "1.9" and "1.11", then delete the line... I am new to perl language. The following is the code I have now... I think I just need to write some code inside the while loop checking if I want to delete the line $dotline before I write to a NEW file.

Code:

#!/usr/bin/perl -w
$TOPPATH = "/tmp";
$NAME = "topology";
$FILENAME = "$TOPPATH/$NAME.dot";

[code]....