# untested
sub bashquote
{
    local $_ = shift;
    defined or die "Argument must not be undef";
    /\x00/ and die "String must not contain NUL characters";
    length or return "''";
    # before adding "/" to safe characters: /^[A-Za-z0-9_]+$/ and return $_;
    m|^[A-Za-z0-9/_]+$| and return $_;
    s/'/'\''/g;
    s|((?:'\\''){2,})|q{'"} . (q{'} x (length($1) / 4)) . q{"'}|ge;
    $_="'$_'";
    s/^''//;
    s/''$//;
    return $_;
}