Reformatted example:

for $i ( 0 .. $#p2 ) {

    #print "$p1[$i] vs $p2[$i]\n";
    $mism_pos{$i} = 1 if ( $p1[$i] eq $p2[$i] );
}

#print sort keys %mism_pos,"\n";
if ( keys %mism_pos ) {
    for $i ( 0 .. $#p2 ) {
        if ( defined $mism_pos{$i} ) {
            if ( @new1 && @new2 ) {
                push @new, @new1, 'and', @new2, $p2[$i];
                @new1 = ();
                @new2 = ();
            }
            else {
                push @new, $p2[$i];
            }
        }
        else {
            push @new1, $p1[$i];
            push @new2, $p2[$i];
        }
    }
}
[download]

The code isn't better but it looks a bit better. This makes live easier.

If you are using vim look here.

If you are using emacs type:

C-x h
esc 1 esc |
[download]

In the minibuffer you will see: Shell command on region:

Type perltidy (assuming you installed it) and press ENTER.