package My::FieldMap; our %INTERNAL_VALUES = ( 'foo|bar' => 'fb_val' ); our %INTERNAL_NAMES = ( 'foo|bar' => 'fb_val' ); sub _build_key { return lc( join '|', @_); } sub get_internal_name_value { shift if $_[0] eq __PACKAGE__; # Can call as pkg method my $ext_name = shift; my $ext_value = shift; my $composite_key = _build_key( $ext_name, $ext_value ); # probably want to put some error checking code here. # What do you do if called in scalar context? # What if one or both keys don't exist? return ( $INTERNAL_NAMES{$composite_key}, $INTERNAL_VALUES{$composite_key} ); }