We need more details for a good answer, e.g. you didn't show us your set() routine.

From the example demonstrated I'd say use $par{margin} and set it to the users input, like -horizontal

another approach is to grep a list of parameters, and take the first positive

($actual) = grep { $par{$_} ne "a" } qw/margin-left margin-horizontal margin/

(that's actually better done with first from List::Util )

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

update

debugger-demo with perl -de0 

  
  DB<21> $par{"margin-left"} = "a" 

  DB<22> ($actual) = grep { $par{$_} ne "a" } qw/margin-left margin-ho
+rizontal margin/

  DB<23> p $actual
margin-horizontal

[download]

update

If you need to do it for different head-parameters like "padding" and so on, try

$chain{margin}    = [qw/margin-left margin-horizontal margin/ ];
# etc
($actual{$head}) = grep { $par{$_} ne "a" } @{ $chain{$head} };

[download]

and let $head loop over "margin", "padding", a.s.o.

In reply to Re: Deferring variables by LanX
in thread Deferring variables by Chuma

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