You don't seem to understand the clues given to you by Corion.

You're basically looking for "From" and "Subject" on the same line, which usually does not occur in emails. Change your logical and to a logical or, and you'll match lines having "From" and lines having "Subject".

In other words, try to change:

while (my $line = <$fh>){ 
    if ($line =~ /From\:/ && $line =~ /Subject\:/) { 
        print $line; 
    } 
}
[download]

To something like:

while (my $line = <$fh>){ 
    if ($line =~ /From\:/ or $line =~ /Subject\:/) { 
        print $line; 
    } 
}
[download]

Update: And since, as mentioned above by ww above, there is no need to escape colons, you could simplify it this way:

while (my $line = <$fh>){ 
    if ($line =~ /From:/ or $line =~ /Subject:/) { 
        print $line; 
    } 
}
[download]