for (grep /^default_option_/, keys %def) {
   my (undef, $option) = split /_/, $_, 2;
   $s{$option} = $def{$_};
}

[download]

... changes to a somewhat dense form of ... 

for ( grep /^default_option_/, keys %def ) {

   $s{ (split /_/, $_, 2)[-1] } = $def{ $_ };
}

[download]

... put other way (by way of moritz's explicit hint) ... 

%s =
  map
  { (split /_/, $_, 2)[-1] => $def{ $_ } }
  #  Useless use of grep.
  grep /^default_option_/, keys %def
  ;

[download]

... which begs to go to the original version despite OP's request... 

%s =
  map
  { m/^ default_ (option_.+) $/x
    ? ( $1 => $def{ $_ } )
    : ()
  }
  keys %def ;

[download]

I, myself, would not have bothered with any of map-grep or for-grep versions shown thus far. In case of for-loop, I would be prone to write "next if".

In reply to Re^2: get solution as short as possible by Anonymous Monk
in thread get solution as short as possible by Anonymous Monk

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