perl - calling a function which may exist within a package -

i have script parse list of packages. actual list of packages not known till run time. some of these packages have couple subroutine. name of subroutine fixed (prebuild , postbuild). having trouble invoking these sub-routines. below code illustrates attempts. question is: how call function may exist, while ignoring when doesn't.

foreach $p (@pkglist) {   $funcname="$p::prebuild";   ## 1. doesn't work. never defined   if (defined (&$funcname)) {    &$funcname   }   ## 2. cops out first time hits packet without subroutine   if (ref (&$funcname) eq "code") {    &$funcname   }   ## 3. same 2.   eval $funcname } 

perl provides universal base class packages, , universal provides can(subname) method. can test availability of arbitrary functions in arbitrary packages.

sub foo::foo { 42 } sub baz::foo { 19 } foreach $pkg (qw(foo bar baz quux)) {     if ($pkg->can('foo')) {         print "foo in $pkg: ", $pkg->foo(), "\n";     } else {         print "foo in $pkg: not found\n";     } } 

output:

foo in foo: 42 foo in bar: not found foo in baz: 19 foo in quux: not found