As others commented, you should probably move the open out of the while loop. You also need to save the matched values in some variables. In your case I would do it like this:

open (OUT,">Test")|| die;
while (<>){
 /^Sen = (\S+)/ && do {$sen=$1};
 /^Acc = (\S+)/ && do {$acc=$1};
 /^Cor = (\S+)/ && do {$cor=$1;
   push @array,$sen,$acc,$cor;
   $sen=$acc=$cor=undef;
 };
}'
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Only if you encouter a "Cor" line (the last one of a block) handle the values you accumulated. And don't forget to clear them, just in case your input file is missing some lines.