how does qx select a "/bin/sh equivalent"?

bronto has asked for the wisdom of the Perl Monks concerning the following question:

Dearest monks and nuns.

Recently I have been bitten by an unexpected behaviour of a commercial software. In short, if I started a daemon with qx in a perl script, it failed to work properly.

I am still investigating. Anyway, it seems that the daemon fails to work properly if it doesn't run under a "classic" Bourne shell, while qx runs it inside a Bash shell.

The following script:

#!/usr/bin/perl

use strict ;
use warnings ;

my $output = qx'echo $SHELL' ;

print $output ;
[download]

returns

/bin/bash

The man page for qx says:

      qx/STRING/
      ‘STRING‘
              A string which is (possibly) interpolated and then exe-
              cuted as a system command with "/bin/sh" or its equiva-
              lent.[...]
[download]

This leads me to the question: how does qx select the aforementioned "/bin/sh equivalent"?

Ciao!
--bronto

In theory, there is no difference between theory and practice. In practice, there is.

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