my %exs;
$file[ $_ ] =~ m[\s+EX\s+[^,]+,(\S+)] and push @{ $exs{ $1 } }, $_ for 0 .. $#file;

##</code><code>##

for my $rtn ( keys %exs ) {
    my $n = 0;
    ++$n until $file[ $n ] =~ m[$rtn\s+(\S+)];
    my $subst = $1;
    $file[ $_ ] = "\t$subst" for @{ $exs{ $rtn } };
}