perl: Post-install XML::Parser and XML::SAX for Linuxbrew (#1209)
perl: Post-install XML::Parser and XML::SAX for Linuxbrew (#1209)

CPAN modules installed through the system package manager will not
be visible to brewed Perl, which means that brewing Perl can cause
previously resolved CPAN requirements to become unresolved.

As a temporary fix, install the 2 most important Perl modules
needed by Homebrew after brewing Perl.

XML::Parser needs expat, so add that as a dependency too.
LinuxbrewTestBot/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,maxim-belkin/homebrew-core,Linuxbrew/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core,maxim-belkin/homebrew-core