回勾使用/bin/sh（或cmd），而不是bash，因此需要构造一个POSIX shell命令，当然，该命令可以调用bash。
以下代码实现了这一点，同时还修复了code injection错误：

use String::ShellQuote qw( shell_quote );

my $sort_cmd1 = shell_quote( "sort", "--", $file1 ) . ' 2>&1';
my $sort_cmd2 = shell_quote( "sort", "--", $file2 ) . ' 2>&1';
my $bash_cmd  = shell_quote( "comm", "-1", "-3" ) . " <( $sort_cmd1 ) <( $sort_cmd2 )";
my $sh_cmd    = shell_quote( "bash", "-c", $bash_cmd );

my $output = `$sh_cmd`;

或

use String::ShellQuote qw( shell_quote );

my $bash_cmd = 'comm -1 -3 <( sort -- "$1" 2>&1 ) <( sort -- "$2" 2>&1 )';
my $sh_cmd = shell_quote( "bash", "-c", $bash_cmd, "dummy", $file1, $file2 );

my $output = `$sh_cmd`;