Your basic problem is you're trying to do more stuff under a statement consisting only of next, the code underneath it won't ever be executed.

Second, you seem to be testing whether a line contains nothing but ");" with a bare if. Newsflash: ");" as a string has a true value. You need a better test. And "=" is not the proper comparison operator.

The following code would appear to do what you want:

while ($string=<IN>)
{
    if ($string=~ /^FIELD/)
    {
     while($line=<IN>) {
        last if $line =~ /^\);$/;
        }
    }
    else
    {
        @lines=split(/\s+/,$string);
        print "@lines\n";
    }
}
[download]

Something else to reconsider: Apparently you treat ");" on a line of its own as special. Perhaps you should reconsider setting $/ to it, treating it as a "line" terminator? That might make things easier.

local $/ = ");\n";
local $\ = $/;
while ($string=<IN>)
{
    if ($string=~ /^FIELD/)
    {
        # no need to skip anything, everything is in $string
    }
    else
    {
        chomp $string;  # get rid of trailing ");"
          # print will add it again, thanks to $\ 
        @lines=split(/\s+/,$string);
        print "@lines\n";
    }
}
[download]