This piece of code could be a starting point. Also look at Re: Convert Tcl Keyed List to Perl where I use the same technique in a different context.

# node 1030367
use strict;
use warnings;
my $expr = '(A&(B&C)|((C&D)|\((A EQ 1)))';

my $level  = 0;
my $tab    = "| ";
my %action = (
        '('       => sub { print "\n", $tab x ++$level, shift },
        ')'       => sub { print "\n", $tab x $level--, shift },
        'default' => sub { print shift },
        );

( $action{$_} // $action{'default'} )->($_) for $expr =~ /./g;
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