use v5.12; use warnings; use Data::Dump qw/pp dd/; my %def = ( 'margin-left' => 'margin-horizontal', 'margin-horizontal' => 'margin', # ... ); my %par = ( 'margin' => 42, ); sub get { my $key = shift // return "UNDEFINED"; # or whatever error mechanism you prefer $par{$key} // get( $def{$key} ) } say get("margin-left"); # 42 $par{'margin-horizontal'} = 666; say get("margin-left"); # 666 undef $par{'margin-horizontal'}; say get("margin-left"); # 42 say get("TYPO"); # UNDEFINED