$ echo some_command a={1,2},{3,4}
some_command a=1,3 a=1,4 a=2,3 a=2,4

##</code><code>##

$ echo some_command 'a={1,2},{3,4}'
some_command a={1,2},{3,4}

##</code><code>##

sub text_to_sh_literal {
   my ($s) = @_;
   s/'/'\\''/g;
   return "'$s'";
}

my $arg_lit = text_to_sh_literal($arg);
`some_command $arg_lit`

##</code><code>##

open(my $fh, '-|', 'some_command', $arg);
<$fh>