Tinkering with Perl

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If-then-else chains

There is one more step to be taken with if-then-else. That is demonstrated by the following segment of code:

if ($Pet == "dog")
    {
    print "Arf, arf!\n";
    }
elsif ($Pet == "cat")
    {
    print "Purr, purr!\n";
    }
elsif ($Pet == "goldfish")
    {
    print "Splish, splash!\n";
    }
else
    {
    print "I don't know what sound the pet makes.\n";
    }

Sometimes, you have more than two choices to deal with -- there are more than two (or three) possibilities for a pet. An if-then-else chain is ideal for the following; the program checks if the first condition is true, and if the first condition is false, it checks if the second condition is true, and so on and so forth. The general syntax is:

if (first conditional clause)
    {
    code to be executed
    if first conditional clause is true
    }
elsif (second conditional clause)
    {
    code to be executed if first
    conditional clause is false, but
    second conditional clause is true
    }
...
elsif (last conditional clause)
    {
    code to be executed if all but the
    last conditional clauses are false, but
    the last conditional clause is true
    }
else
    {
    code to be executed if none of the
    conditional clauses are true.
    }

The final else is optional, but recommended.

Tinkering with Perl

If-then-else chains

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