while (<FILE>) {
   if (/.../) { 
     ... 
   }
}

##</code><code>##

my $stuff;

while (<FILE>) {
   if (/(...)(...)/) {
      # we have $1 and $2 in here, both some string
   } elsif (/(...)/) {
      $stuff = $1;
   }
}

##</code><code>##

eval "\$$stuff{$1} = $2";