my $arrayHash1 =();
my $arrayHash2 =();
my $arrayHash3 =();
my $FinalMegaHash =();

if ( condition1==true){
generate arrayHash1;
$FinalMegaHash .= $arrayHash1;
}
if ( condition2==true){
generate arrayHash2;
$FinalMegaHash .= $arrayHash2;
}
if ( condition3==true){
generate arrayHash3;
$FinalMegaHash .= $arrayHash3;
}
print Dumper $FinalMegaHash;