my $func_Ref = \&$self->isInst;
foreach my $var ( @something ) {
    &$func_Ref( $self, $var )
}

##</code><code>##

my $func_Ref = \&$self->isInst;
foreach my $var ( @something ) {
    $func_Ref->( $self, $var );
}

##</code><code>##

my $func_Ref = \&$self->isInst;

$func_Ref->( $self, $_ ) for @something;