You seem to also want indentation with "\t", which means you need to keep count of the loop levels.

Here a much easier to maintain code, looping over a split and keeping track of indentation.

And you can easily adapt this code to emit other languages - like Perl° - too, without worrying about polluted input.

use strict;
use warnings;
#use Data::Dump qw/pp dd/;
#use feature qw/say/;

my @table = split /\n/, <<'__TABLE__';
>    ++k;
<    --k;
+    ++*k;
-    --*k;
.    putchar(*k);
,    *k = getchar();
[    while (*k) {
]    }
__TABLE__

my %trans = map { split/\s+/, $_, 2 } @table;
#pp \%trans;



my $bfs   = '+[--[--]->+++<]>+.---';
my $level = 0;

for my $atom ( split //, $bfs ) {

    $level-- if $atom eq "]";
    print "\t" x $level;
    $level++ if $atom eq "[";
    
    print $trans{$atom};
    #print "\t\t\t// was '$atom'";         # debug
    print "\n";
}
[download]

++*k;
while (*k) {
    --*k;
    --*k;
    while (*k) {
        --*k;
        --*k;
    }
    --*k;
    ++k;
    ++*k;
    ++*k;
    ++*k;
    --k;
}
++k;
++*k;
putchar(*k);
--*k;
--*k;
--*k;
[download]

update

°) which would allow you to use the perldebugger to step thru BF code.

update

changed code to improve readability