Close. 

my $expr =
   join '|',
      map { keys( %{ $replaces{$_} } ) }
         keys( %replaces );

[download]

With foreach: 

my @keys;
for ( keys( %replaces ) ) {
   push @keys, keys( %{ $replaces{$_} } );
}

my $expr = join '|', @keys;

[download]

In reply to Re: One-liner to join keys on a two-dimensionnal hash ? by ikegami
in thread One-liner to join keys on a two-dimensionnal hash ? by Anonymous Monk

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