...
my $zeilennummer = $param_zeilennummer || 0;
my $ist_ok = $param_ist_ok || 0;

my $skip;
$skip = <$input> for (0..$zeilennummer);
if ($ist_ok) {
    mach_was($skip);
}
my $zeile = <$input>;
print ...HTML... <a href=...?zeilennummer=$zeilennummer+1&ist_ok=1>...