The following code may be found in Term::ReadLine:

my ($which) = exists $ENV{PERL_RL} ? split /\s+/, $ENV{PERL_RL} : unde
+f;
if ($which) {
  if ($which =~ /\bgnu\b/i){
    eval "use Term::ReadLine::Gnu;";
  } elsif ($which =~ /\bperl\b/i) {
    eval "use Term::ReadLine::Perl;";
  } else {
    eval "use Term::ReadLine::$which;";
  }
} elsif (defined $which and $which ne '') {     # Defined but false
  # Do nothing fancy
} else {
  eval "use Term::ReadLine::Gnu; 1" or eval "use Term::ReadLine::Perl;
+ 1";
}
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I think this is similar to what you are looking for.