cr

my %DISPATCH = (
    BOOTPROTO => sub { $_[1] = '"static"';
                         return join '=', @_; },
    IPADDR    => sub { return setValueForField('IPADDR', @_) },
    NETMASK   => sub { return setValueForField('NETMASK', @_) },
    GATEWAY   => sub { return setValueForField('GATEWAY', @_) },
    DNS1      => sub { return setValueForField('DNS1', @_) },
    DNS2      => sub { return setValueForField('DNS2', @_) },
);

for my $line (@array) {
    my @fields = split /=/, $line;
    my $sub = $DISPATCH{ $fields[0] } or next;
    $line = $sub->( @fields);
}