[Perl5-tut] Perl Intro: Conditionals

[wtd]

If

This looks pretty much like most languages. A notable differences is that the curly braces are required. There is no "shortcut" syntax.

Perl:

if ($foo == 42) {    print "Hello\n"; }

Elsif and else

As in other languages, there are fallback clauses.

Perl:

if ($foo == 42) {    print "Hello\n"; } elsif ($bar == 38) {    print "Yo\n"; } elsif ($baz == 56) {    print "Wooble!\n"; } else {    print "Ninja!!!\n"; }

Unless

"if" has a counterpart. It's called unless.

For instance, instead of:

Perl:

if ($foo != 42) {    print "Hello\n"; }

We can write:

Perl:

unless ($foo == 42) {    print "Hello\n"; }

Postfix

For very simple tests, we can use "if" and "unless" in a postfix form.

Perl:

print "Hello\n" unless $foo == 42;

The ternary operator

This also functions pretty much the same way it does in other languages.

Perl:

$foo == 42 ? "Hello" : "World";

If the test in front of the question mark is true, then the first expression is evaluated. If not, the second expression is evaluated. The expressions are separated by a colon.

Comparison operators

Strings and numbers use different comparison operators in Perl5.

For numbers, we can use the classic: ==, !=, <, >, <=, >=, and for a three way comparison: <=>.

For strings, the corresponding operators are: eq, ne, lt, gt, le, ge, and cmp.