[mercury-users] Perl shift || $defalt

[Terrence Brannon]

In Perl, it is very easy to say the following:

  the value of x is equal to the first data item in ARGV, 
  or if ARGV is not defined then use the value 12:

$x = shift || 12;
print "$x\n";

Thus, a program can either take values on STDIN or use hardcoded
defaults with relative ease.

Could someone show how to do this same thing in Mercury? 

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