$ ./1.MY.translate.pl
Can't locate My/Module.pm in @INC (you may need to install the My::Module module) (@INC contains: /home/bob/perl5/lib/perl5/x86_64-linux-gnu-thread-multi /home/bob/perl5/lib/perl5 /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.26.1 /usr/local/share/perl/5.26.1 /usr/lib/x86_64-linux-gnu/perl5/5.26 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.26 /usr/share/perl/5.26 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base) at ./1.MY.translate.pl line 23.
BEGIN failed--compilation aborted at ./1.MY.translate.pl line 23.
$ cat 1.MY.translate.pl
#!/usr/bin/perl -w
use 5.011;

package My::Module;

sub new {
  my ( $class, $param_hr ) = @_;
  $param_hr = {} unless defined $param_hr;
  my $self = {    # hashref or arrayref
    key    => 0,
    format => 0,

  };
  bless $class, $self;    # now your hash is an object of class $class.
  if ( exists $param_hr->{'key'} ) { $self->key( $param_hr->{'key'} ) }
  else { warn "param 'key' is required."; return undef }
  return $self; # return the hash, now blessed into a class instance, hallelujah
}

1;

package main;
use My::Module;

# the notation module->new adds "module" as the first argument to the new() params.
# so here is how $class is set in your question, although YOU dont pass class, Perl does.
my $mod = My::Module->new(
  {
    'key' => 123,
  }
);
die unless defined $mod;

# the same notation applies when calling the method
# Perl passes the object ref ($self=$mod) to the method as a first param
print "my key: " . $mod->key() . "\n";

$