I want something like MIME::Base64, but only using lower case letters and numbers. In fact a base 32 encoding would be just fine ( which uses 32 of the 26 + 10 = 36 possible characters ). The aim is to turn hash keys into well behaved file names. Here is my solution: 
my $string="foobar";

my $base32;

my $bin=unpack 'B*',$string;

print "string: $string\nbin: $bin\n";

print "original length of bin: ",length($bin),"\n";

my $bm5=length($bin) % 5;

$bin=($bm5?('0'x(5-$bm5)):'').$bin;

print "corrected length of bin: ",length($bin),"\n";

while($bin=~s/(.....)//)
{    
    my $dec=oct('0b'.$1);
    
    $base32.=$dec<26?chr(ord('a')+$dec):chr(ord('0')+$dec-26);
}

print "base32: $base32\n";

print "length of base32: ",length($base32),"\n";

[download]
prints: 
string: foobar
bin: 011001100110111101101111011000100110000101110010
original length of bin: 48
corrected length of bin: 50
base32: dgn3xweyls
length of base32: 10

[download]

In reply to How can I encode a string using only lower case letters and numbers? by tkguifan

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