use strict;

...
blah
...

my $count=0;
foreach (@spalten_filter) {
if ($spalten_filter[$count] =~ s/^mittel_/summe_/) {
$zeile_file[$filter[$count]]=$zeile_file[$filter[$count]]*($zeile_file[$index_zeit_summe_intervall]/3600);
}
$count++;
}