Thanks so so so much for your help! The situation is complicated and i'm new in "Perl"! Then: if i print "array_with_all_fields4" this is my output:

GO:0000060 GO:0000122 GO:0000979 GO:0001077 GO:0001701 GO:0001756 GO:0001836 GO:0002309 .....

After i store this output into "mio" for a particular need. After i store "mio" into an hash table as the keys of the hash table. If i print the hash table this is the output:

$VAR1 = 'GO:0000060'; $VAR2 = ''; $VAR1 = 'GO:0000122'; $VAR2 = ''; $VAR1 = 'GO:0000979'; $VAR2 = ''; $VAR1 = 'GO:0001077'; $VAR2 = ''; $VAR1 = 'GO:0001701'; $VAR2 = ''; .....

the final step for me is to store keys into an array "test2" and after use this array in another "while" and in another "FILE2".

I know that is so difficult to explain but if you want i can write to you from my personal mail!

Thaks a lot Paola