First think filehandles. And you will need to see the listing of << < >> > +<< etc.
I think it is easier to deal with chunky bits of text, run some regex etc. The while{} is initializing $line with a chunk of new text terminated by \n (and carriage return linefeed I think). If I had an address in variable $content like .. = "c:/temp/text.txt" then open would have
open(my $fh1, "<", $content). If I wanted to actually parse the contents of a variable like $content = "a lot of text strings etc packed in a variable" then I would send a reference like
open(my $fh1, "<", \$content).
Make sure you close it when done.
open(my $fh1, "<", \$content) or die('can not open content');
while (my $line = <$fh1>) {
do something with $line
}
close($fh1);