my($foo, $bar) = (1,2);
my @vars = \($foo, $bar); # note the backslash before the list
# this would do the same: my @vars = (\$foo, \$bar);

foreach my $var (@vars) {
    $$var += 4; # note the de-referencing $ before $var
}
print "\@vars: @vars\n";
print "\$foo: $foo\n";
print "\$bar: $bar\n";
__END__
@vars: SCALAR(0x15ae7a0) SCALAR(0x15ae830)
$foo: 5
$bar: 6