while ( @acc_list ) {
 ...
 my @files1 = splice( @acc_list, 0, 100 );
 ...
}

##</code><code>##


for( my $p = 0; $p < @acc_list; $p += 100 ) {
    ...
    my @files1 = @acc_list[ $p .. $p+99 ];
    ...
}