Pretty print a tree structure in ascii using box drawing chars

test_pp_tree.pl

use strict;
use warnings;
use feature 'say';

use Data::Dumper;

# Pretty print a tree structure

# Constants for drawing lines and spaces
my $_cross = "├─";
my $_corner = "└─";
my $_vertical = "│ ";
my $_space = "  ";

# test struct
my $struct = { node => 'Top level',
               childs => [
                   { node => 'prequel', childs => [
                   { node => 'first',
                     childs => [
                         { node => 'one' },
                         { node => 'two' , childs => [{ node => 'brol'}]},
                         { node => 'three' }
                         ]
                   },
                   { node => 'second'
                   },
                   { node => 'third',
                     childs => [{ node => 'foo'}]
                   }
                         ]},
                   { node => 'sequel' }
                   ]
};
# $struct = { node => 'alone', childs => [ { node => 'single'}] };


say(show_tree(prefix => '', data => $struct, islast => 1));

sub show_tree {
    my %args = @_;
    my $ret = '';
    # my $sub_indent;
    my $indent = $args{indent} // '';
    my $level = $args{level} // 0;
    
    # prefix
    $ret = $args{prefix};

    # indent
    $ret .= $indent;
    
    if ($args{islast}){
        $ret .= $_corner if $level > 0; # only for non-top (avoid corner for top level)
        $indent .= $_space if $level > 0;
    } else {
        $ret .= $_cross  if $level > 0; # only for non-top (avoid corner for top level)
        $indent .= $_vertical;
    }
    $ret .= $args{data}->{node};
    $ret .= "\n";

    return $ret unless exists $args{data}->{childs};
    
    my $child_count = scalar @{$args{data}->{childs}};
    for (my $i = 0; $i < $child_count; $i++){
        my $child = $args{data}->{childs}->[$i];
        my $islast = ($i == $child_count - 1);
        $ret .= show_tree(prefix => $args{prefix}, data => $child, indent => $indent, islast => $islast, level => $level + 1);
    }
    return $ret;
}