If you have two submit buttons on the same form you will need to check which one was clicked

use CGI;
my $q = CGI->new;
my $bA = $q->param('button_A');
my $bB = $q->param('button_update');

if($bA eq "whatever") {
    # do whatever
}

if($bB eq "Update") {
    # do update stuff here
}
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