Avoid the shell and you avoid the need for shell quoteing

#!/usr/bin/perl --
##
##
## perltidy -olq  -csc -csci=3 -cscl="sub : BEGIN END " -otr -opr -ce 
+-nibc -i=4 -pt=0   "-nsak=*"
## perltidy -olq  -csc -csci=10 -cscl="sub : BEGIN END if " -otr -opr 
+-ce -nibc -i=4 -pt=0   "-nsak=*"
## perltidy -olq  -csc -csci=10 -cscl="sub : BEGIN END if while " -otr
+ -opr -ce -nibc -i=4 -pt=0   "-nsak=*"
#!/usr/bin/perl --
use strict;
use warnings;
use Digest;
use Digest::MD5;
use Path::Tiny qw/ path tempfile tempdir cwd /;
use File::Find::Rule qw/ find rule /;

Main( @ARGV );
exit( 0 );

sub Main {

## self test
#~     warn  mmd5external( __FILE__ );
#~     warn  mmd5perl( __FILE__ );
#~     warn  mmd5( __FILE__ );

#~     rule( 'file' )->exec( \&Famatte )->in( '/tmp' );
#~     find( 'file' => 'exec' => \&Famatte , in => [ '/tmp' ] );
    rule( 'file' => 'exec' => \&Famatte, )->in( '/tmp' );
} ## end sub Main

sub Famatte {
    my( $shortname, $path, $fullname ) = @_;
    RealFamatte( $fullname );
    return !!0;    # discard filename
} ## end sub Famatte

sub RealFamatte {
    my( $filename ) = @_;
    print mmd5( $filename ), "\t$filename\n";
} ## end sub RealFamatte

sub mmd5 {
    goto &mmd5perl;

#~     goto &mmd5external;
} ## end sub mmd5

#~ sub mmd5external {
#~     use File::Which qw/ which /;
#~     use Capture::Tiny qw/ capture /;
#~     my( @args ) = @_;
#~     my $cmd = which('md5sum');
#~     my( $stdout, $stderr, $exit ) = capture {
#~         system( $cmd, @args );
#~     };
#~     if( $exit ){
#~         warn "uhoh got error exit( $exit ) : $stderr ";
#~     } else {
#~         $stdout =~ s/\s+$//; ## "chomp"
#~         return $stdout;
#~     }
#~ }

sub mmd5perl {
    my $fh  = path( shift )->openr_raw;
    my $ctx = Digest->new( 'MD5' );
    $ctx->addfile( $fh );
    return $ctx->hexdigest;
} ## end sub mmd5perl
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perltidy, Digest, Digest::MD5, File::Find::Rule, Path::Tiny, File::Which, Capture::Tiny.

Path::Tiny, find/rule